on the contractility and innervation of the spleen

ON THE CONTRACTILITY AND INNERVATION OFTHE SPLEEN1. By E. A. SCHAFER, F.R.S., AND B.MlOORE. (Forty-two Figures in Text.)

(From the Physiological Laboratory, Untiversity College, London.)

CONTENTS.Historical. pp. 1-5.Method. pp. 5-8.Normal movements of spleen. pp. 8-11.Influence of nerves: pp. 11-18.

splanchnics.vagi.splenic nerves.

Independence of splenic rhythm. pp. 19-23.Effect of drugs upon movements of spleen. pp. 23-28.Effect of dyspntsa and ansmia. pp. 29-36.The connexions of the splenic nerves with the spinal cord. pp. 37-39.The ganglion-cell connexions of the splenic nerves. pp. 40-49.Conclusions. p. 50.

Historical.

THE contraction of the spleen on direct stimtulation was first observedby Rudolph Wagner in the dog (1849). Henle2 (1852) showedthat this organ possesses contractility in man. Schiff3 (1867) ob-tained contraction of the spleen in rabbits and cats on stimulation ofthe splanchnic nerve and of the semilunar ganglion. Sabin sky4 (1867)showed that after death from asphyxia the spleen is constantly foundin a contracted and anaemic condition. He came to the conclusion asthe result of his experiments that this was not duie to the direct actionof asphyxial blood upon the organ but that the effect was a reflex oneand dependent upon the integrity of the nerves to the organ. Oehl5

1 Preliminary accounts of these investigations were communicated to the Royal Societyon Jan. 30, 1896 and on February 26, 1896 and have been published in its Proceedings.

2 Zeitsch. f. rat. Med. N. F. ii. 299.3 Le5ons sur la physiologie de Id digestion. T. ii.4 Vierteljahrsschriftf. gerichtl. Med. N. F. i.5 Gaz. Lomb. 1869.

PH. XX. 1

E. A. SCHHAFER AND B. MOORE.

(1869) obtained contraction of the spleen on stimulation of the peripheralend of either vagus in the neck in dogs, rabbits and cats. Bu lgak'(1877) made a series of carefully conducted and systematic observationsuipon the contractility and innervation of the organ, employing as hadbeen done by his predecessors the method of direct observation. Heused young full grown dogs as being better adapted than any otheranimals for the purpose a statement in which we entirely concur; theywere narcotised by intravenous injection of morphia. He gives a carefuldescription of the anatomical connections of the organ with nerves, someof which he found to be sensory. He further states that the sensorynerves run apart from the motor. He confirms a statement of Mosler'that large doses of quinine (5 to 6 grains) caused contraction of the organ,a result he was unable to obtain with ergot. He confirms Sabinsky'sobservation that asphyxia always produces strong contraction of thespleen. He states in opposition to Oehl that stinmulation of the peri-pheral end of the cut vagus produces no contraction of the organ. Thisexperiment he performed both upon the cervical and upon the thoracicvagus. He points out that stimulation of the central end of the vagusproduces a strong contraction of the spleen and that the same effect isobtained bv stimulation of the central end of the superior laryngeal.He opines that this effect is due to the arrest of respiration whichaccompanies such stimulation.

Bulgak further found that whereas excitation of the spinal cord atthe level of the membrana posterior atlantis produced not the leastcontraction of the spleen, excitation at the level of the lower borderof the atlas and from here down to the level of the 4th cervical vertebracaused a strong contraction of the organ. Also that reflex contractionsof the spleen were obtained equally well after severance of the spinalcord from the medulla oblongata by a section at the level of the membranapostemior atlantis. He obtained some effect upon the spleen by stimu-lating the cord between the 4th cervical and 11th dorsal vertebrae butnone below the level of the 11th dorsal. He is of opinion that a reflexcentre for the spleen is placed in the spinal cord between the level ofthe atlas and that of the 4th cervical vertebra and that the effectsobtained below the last mentioned level are due to stimulation of fibresproceeding to and from this centre. He obtainied strong contraction ofthe organ on stimulating the peripheral end of the left greater splanchnic

1 Virchow's Archiv, LXIX. 181.2 Die Pathologie u. Therapie der Leukiamie. Berlin, 1872.

2

CO:NTRACTILITY OF SPLEEN.

nerve but no effect whatever from the left lesser splanchnic nor fromthe right splanchnics. Lastly he observed contraction of the spleen tofollow stimulation of the cut anterior nerve-roots (apparently on theleft side only) from the 3rd dorsal to the 10th dorsal pairs inclusive, thecontraction being quite distinct althouggh not strong. No other nerve-roots gave any noticeable result. Bulgak comes therefore to theconclusion that the spleen is innervated with both afferent and efferentfibres which are connected with a reflex centre in the ipper part of thecervical cord and which pass to their distribution in the organ by wayof the anterior nerve-roots from the 3rd dorsal to the 10th dorsal andthe greater splanchnic nerves of the left side only; thence through thesemilunar ganglion and by the nerves accompanying the branches ofthe splenic artery. Bulgak's work was originally published in Russianin 1872: it was performed under the direction of Prof. Babuchin.

Tarchanoff' (1874) found that stimulation of the medulla oblon-gata caused an obvious contraction of the spleen and that this occurredthrough either splanchnic.

Roy2 (1881) investigated the changes of volume of the organ bymeans of a modified plethysmograph to which he gave the name ofoncometer or oncograph. Roy found the spleen to be normally subjectto regular alterations of volume (systole and diastole) succeeding oneanother in the case of the dog and cat without intermission at regularintervals of about one minute. The amount of change he found to bevariable in different animals, and under different conditions in t4e sameanimal, being always increased by stimulation of any sensory nerve andby any alteration in the blood-the injection even of a small quantityof salt solution being productive of this effect. Curare is especiallymentioned as producing increase of the rhythmic movements, precededin this case by a temporary expansion of the organ whereas certain otherunspecified substances produce primarily a contraction.

With regard to the influence of nerves upon the organ, Roy statesthat direct stimulation of the vaso-motor centre produces contraction ofthe spleen, and that the same effect is obtained by stimulating theperipheral end of either vagus or either splanchnic. Nevertheless,section of both vagi and both splanchnics does not abolish or per-manently modify the rhythm. From this it was concluded that therhythm is of peripheral origin. This deduction, however, was obviouslymade on insufficient grounds; for the spleen was still connected with the

P,flllger's Archiv, viii. 2 This Joumal, in. 203.

1-2

3

E4 A. SCHIFER AND B. MOORE.

central nervous system by other paths of communication, as the authorhimself points out.

It is fuirther stated by Roy that the spleen curve shows no pulsewave, and very little change of volume corresponding with the respi-ratory changes of blood-pressure: from which he concludes " that thepassages by which the arterial blood enters the spleen are comparativelyvery narrow "-a conclusion which he considers is confirmed by theobservation that if the aorta is closed for a moment at its point ofpassage through the diaphragm the resultant diminution in volume ofthe spleen " takes place very slowly, there is no sudden fall " as in thecase of the kidney, intestine or limb,-" Indeed, when the spleen isexpanding at the moment of closure of the aorta, the lever may remainnearly stationary till the time comes for the commencement of thesplenic systole." This experiment of closing the aorta for a few secondswas repeated " as often as occasion offered."

Far reaching deductions are drawn by the author from these obser-vations. " The very imperfect degree to which the volume of the spleenresponds to variation ini the height of the blood-pressure shows us thatthe mass of the blood in the organ is practically cut off from the arterialsystem, and that therefore the circulation through the organ nmust becarried on almost exclusively, if not exclusively, by the rhythmic con-tractions of the smooth muscular fibres which are found in the spleniccapsule and trabeculae."

It is further noticed that interruptionr of artificial respiration in acurarized aninmal produces great and sudden contraction of the spleen,but whether this is a direct action upon the muscular tissuie of the organor not could not be determined owing to the inability of the author tosatisfactorily divide all the splenic nerves.

The relation of the splenic curves to the Traube-Hering cuirves onthe blood-pressure was carefully considered by Roy, wbo was able toshow that the two curves are independent of one another although ifthe Traube-Hering curves are well marked they may by interferenceproduce a certain appearance of irregularity in the spleen curves.

Since the article by Roy above noticed no further observationsbearing upon the subject have, so far as we have been able to ascertain,been published.

Dr. J. Rose Bradford attempted some years ago, in this laboratory,to determine the spinal-root connections of the spleen with the aid ofRoy's oncometer, but he encounitered considerable difficulties, and theresults which he was able to obtain were inconclusive, He informs

4

CONTRACTILITY OF SPLEEN.

us, however, that he got contraction of the organ on stimulation ofnerve-roots in the thoracic region on both sides, although the limitsof the outflow were not decided, and that there was a tendency togreater contraction on stimulation of the roots on the one side than onthe other.

Method.

The method which we have employed for investigating the contrac-tion of the spleen has been that of the plethysmograph. Very early inour experiments we found that the instrument devised by Roy wasunsatisfactory to work with partly on account of the fact that it wasdifficult to prevent its leaking, and partly because we had reason tobelieve that the blood supply to the organ was interfered with by com-pression at the lips of the oncometer. Indeed, except under very

Diagram of gutta-percha spleen-box.

favourable conditions it appeared to be only capable of showing theslower variations in voluine of the organ. Our spleen-boxes we havemoulded out of gtitta-percha. Each consists of an oblong box withflattened edges upon which a flat plate of glass fits accurately. Theglass cover is kept in position by iindia-rubber bands and rendered air-tight with the aid of vaseline. One side of the box is somewhat lowerthan the others, and through this side (whichl is also kept air-tight by athick layer of vaseline, with the assistarnce, where necessary, of a littlecotton-wool soaked with vaseline) the blood supply to the organ,which is placed within the box upon a layer of cotton-wool, is conducted

5

E. A. SCHAFER AND B. MOORE.

and can remain perfectly free and uninterrupted. A tube leads fromthe box and is connected by an india-rubber tube either with a tambouror with a piston-recorder, the whole apparatus being filled with air.Every variation in the volume of the spleen is accurately followed bythe recording instrument, and a lateral tube leads from the connectingindia-rubber tube and is closed with a clip so that at any momient byopening the clip the pressure may be equalised within and outside theapparatus. The method of preparing the spleen is similar to that usedby Roy; the organ being exposed by a free incision through the ab-dominal wall, and simply placed within the spleen-box. We havesometimes found it to be an advantage to put a double ligatureround the upper or left part of the gastro-splenic omentum, andto sever between the ligatures, for in some animals the spleen istightly tied down to the stomach by its upper end so that it isdifficult without dragging upon the omentum to get it freely withina spleen box. The tying up of this small portion of the omentummakes, however, no practical difference to the physiological conditions ofthe organ. In many of our experiments, we have tied up much more thanthis, and in some observations in which we desired to investigate theconditions of rhythmic contraction of the spleen in the absence of allnervous connections with the body we have tied up by successive doubleligatures all parts of the splenic omentum, leaving only a single arteryand vein in connection with the organ. Indeed in a certain number ofexperiments wve have severed even these, and connected the organ byglass tubes to the body. That this instrument is very much betteradapted than the oncometer for exhibiting all changes in volume of theorgan, may be seen by compar'lson of a spleen curve obtained by it(Fig. 1) with those obtained by Roy's instrument'. In the latter,the respiratory variations in the blood-pressure are only slightlymarked, and the variations due to the heart's beats are scarcelyseen, whereas in most curves obtained by our instruments both thealterations in pressure due to respiration and to ventricular beats arewell marked. In some of our tracings as here reproduced it is difficultto see the individual heart-beats; but this is in consequence of thegreat reduction in size which has been employed in order to bring thetracings within the limits of a page. In the actual tracings in most casesthe heart-beats are well seen upon the spleen-curve, even when thespleen has remained connected with the body by a single artery and veinonly. (Fig. 1 and others.) We must assume, therefore, that the absence

1 This Journal, iii., Plates XV. and XVI.

6

CONTRACTILITY OF SPLEEN. 7

of these fluctuations, which is characteristic of Roy's curves, is due toinstrumental imperfections. At any rate it is not a normal condition,and along with it the theory which regards the circulation of the blood

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arterial blood, falls to the grouind. In fact, it has been abundantlymanifested in our experiments upon the excised organ that a pressurewhich is less than the ordinary arterial pressure of the animal is suffi-cient to carry on the circulation through the organ; and the sameapplies to those cases, which are not rare, in which the rhythmic con-tractions of the spleen are in abeyance. Under these circumstancesthe flow of blood through the organ is still to all appearance perfectlyfree.

Normal Movements.Our observations relate (1) to the normal rhythmic movements

of the organ, (2) to the influence of nerves upon its movements, (3)to the influence of drugs and of varying conditions of the blood uponthose movements and (4) to the connection between the spleen-nervesand spinal cord. With the exception which we have above dwelt uponwe find the normal movements of the spleen much as they were de-scribed by Roy. We find moreover, as might be supposed from thefact that the flucttuations of blood-pressure due to the heart beats andto the respirations are perfectly visible upon the spleen-curve, thatevery variation in blood-pressure is also immediately responded to bythe spleen. The normal movements vary in extent and also in durationbut the latter is frequently about one minute when the spleen is placedin a box such as that used by ourselves or by Roy. But it is pos-sible this may be somewhat slower than when the spleen is inposition in the body, for in all probability the cooling which the organmust undergo, somewhat slows the rate of the rhythm. The rhythmiccontractions are greatly diminished or entirely abolished by chloroform;but they continue normal with morphia alone or with morphia combinedwith atropin, the latter in small doses, sufficient to paralyse the in-hibitory action of the vagi on the heart. They also continue freelyin a curarised animal. Their extent varies from an almost imperceptiblewave to very large and extensive curves. In the former case it wiliusually be found that the spleen generally is in a tonically contractedcondition,and is also less responsive to small changes in the blood-pressure.

It sometimes happens that the curves whicb are seen upon thetracing recorded by the spleen-plethysmograph are exactly synchronouswith curves upon the blood-pressure. This synchronism may be complete,that is to say, the rise of the blood-pressure curve may exactly corre-spond with the rise in the spleen curve (fig. 2); or it may be incomplete,that is to say, while the rhythm is the same, the one curve may berising while the other is falling and vice versa (fig. 3).

8


When the nerves going to the organ are intact fluctuations in sizeof the spleen may occur which correspond exactly to Traube-Hering

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10 E. A. SCHAFER AND B. MOORE.

passively affected by the alterations in blood-pressure. This last is almostcertainly the cause when they occur after all the nerves to the organ are

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spond. In this case the nerves going to the organ were all severed, andthe spleen was connected with the body by a single artery and vein only.In the other curve (Fig. 3) it will be seen that the rise in the spleencurve occurs later than the rise in the blood-pressure curve: thatalthough the rate of rhythm is the same the synchronism is not perfect.Here therefore the changes in volume of the spleen can hardly be pro-duced passively. But on the contrary, in this case the changes iu theblood-pressure curve might be due to the contraction of the spleenraising the pressure in the arteries by forcing with each cottractionmore blood towards the heart. We are, however, unable to produceconelusive evidence to show whether the synchronism of the curves isa mere coincidence or whether they stand in relation to one another ascause to effect: and for the present must leave the qtuestion undecided.

Influence ofr Nerves.

It is known that contraction of the spleen may be brought aboutthrough the central nervous system, and this both reflexly and directly.As already stated it was shown by Tarchanoff, that stimulation of themedulla oblongata produces through the splanchnics an obvious contrac-tion of the organ; and-the fact was confirmed by Roy who showed thatstimulation of either right or left splanchnic in the abdomen produces agreat diminution in the volume of the spleen. We can fully confirmthis result, for our tracings show that stimulation of either splanchnic,provided the nerves going to the organ are intact or even provided thtatonly a single nerve twig is left connecting the spleen with the sympa-thetic system, will produce a marked contraction of the organ (Fig. 4).Of course if the nerves to the spleen are all divided there is only apassive expansion due to the raised blood-pressure resulting from suchstimulation (Fig. 5), and this fact we have used to prove whether allnerves have been divided or not. We have endeavoured by stimulat-ing the splanchnics above the diaphragm with slow stimulations at therate of one or two per second, or with weak stimulations, to determinewhether such excitation of these nerves might produce dilatation insteadof contraction of the organ. Only in a single animal have we succeededin obtaining positive results, most of our results, under these circum-stances, having been negative. In the case in question, of which wegive the tracing in Fig. 6, we found that whereas a strong and rapidexcitation of the left splanchnic produced the usual marked contractionand diminution in volume of the organ, a weak excitation tended to

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produce the reverse effect, namely a general dilatation of the organcombined with an increase in the extent of its rhythmic contractions.

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safe in inferring that the splanchnics contain not only fibres which tendto provoke a contraction of the muscular fibres of the organ, but alsoothers which tend to inhibit that contraction. The existence of suchinhibitory or dilatator fibres is further rendered probable by an experi-ment upon the nerves of the excised and perfused spleen which willpresently be alluded to (p. 22).

It is stated bv Oehl and by Roy that stimulation of the peripheralend of either pneumogastric nerve will also produce strong contractionof the spleen. It does not seem to have occurred to these observersto abolish the inhibitory action of the vagus upon the heart by atropinbefore attempting this experiment; but Roy is content to point outthat the contraction which he obtained is much greater than might beexpected by supposing that the contraction of the organ was passivelydue to a fall in the blood-pressure resulting from inhibition of the heart.

On this point our results are in entire contradiction to those of Oeh 1and Roy and fully confirm the statements of Bulgak. We have neverobtained by stimulation of the peripheral end of the cut pneumogastricnerve any contraction of the spleen. We have got in one or two in-stances a slight effect upon the recording lever of the plethysmograph:but no more than would be produced by the strong contraction of thecesophageal and gastric muscular fibres which result from stimulation ofthe peripheral end of this nerve, and which would tend to drag uponthe gastro-splanchnic omentum, and so to pull upon the hilum of theorgan. In many cases we have been able entirely to avoid such drag.Under these circumstances there is absolutely no effect whateverobtained upon the volume of the spleen. And even in those caseswhere a drag was obvious the only effect experienced was slight diminu-tion in the extent of the excursions of the organ. We have done thisexperiment both in the dog and in the cat; and since the matter is oneof some importance and different results have been obtained by otherworkers, we give tracings which show the negative results obtained(Fig. 7 and Fig. 8 A). It is true that in our experiments we haveadministered a small amount-about five milligrammes-of atropin inorder to obviate the effects which would otherwise be produced uponthe heart and this drug was not used by Oehl and Roy; but as all ourexperiments show that such a dose of atropin, and even a dose consider-ably larger than this, produces no effect either upon the splenic rhythmor upon the action of any of the nerves which pass to the spleen, wecannot believe that the difference between our result and that obtainedby Roy is to be accounted for by supposing it to be due to the employ-

14


ment of this drug. We can only infer that in other cases the electricexcitation was allowed to spread either to the upper end of the vagus,

FIG. 7. Negative effects of stimulating the peripheral end of the cut vagusin a cat. Three milligrams of atropia sulphate had been given to paralyzeinhibitory fibres to heart. jr.

in which case a marked contraction of the spleen is obtainied (Fig. 8 B)or to some other sensory nerve; for the tracing given by Roy asillustrative of his result is exactly the kind of tracing, which may be gotby reflex excitation of the organ through the central nervous system.As we have previously shown, Bu lgak stimiulated the vagi (peripheralend) both in the neck and in the thorax; in the latter case avoidingthe cardiac inhibitory fibres. His results were, like our own, entirelynegative as regards the spleen.

We have further invariably found that stimuilation of any of thenerves accompanying, the arterial branches to the hilum produces amarked contraction of the organ.

An example of this effect is shown in the tracings (Figs. 9 and 10) inwhich the spleen was connected with the body by one artery and veinonly, all the other tissue connections being severed. The nerves accom-panying, this artery and vein, having been previously tied with a ligature,were placed upon electrodes and stimulated and the strong contractionof the organ was obtained which is shown in the tracings. In Fig. 10the effect of such contraction in producing an after increase in therhythmic movements of the organ is well displayed.

15

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Independence of the splenic rhythm.

Although the contractions of the spleen are unquestionably in-fluenced through the nervous system; responding as they do by anincrease of extent of the movement to every stimulation of an afferentnerve (see especially Fig. 8 B), never-theless they will continue even when b

the organ is entirely cut off from allconnection with the central nervoussystem. The first method by whichwe endeavoured to determine thisquestion was to sever all the nerves lpassing to the spleen and to leave l -

the organ connected only by its bloodvessels. We soon found, that it was mdifficult if not impossible to be sure ofeffecting this result if we endeavouredto preserve a large number of the bloodvessels. Since, however, all the fluctua- ltion's in volume of the organ which areproduced by variations in blood-pressureand by its rhythmnic contractions, areperfectly well shown even when thespleen is connected with the body bya single artery and vein, the question o o

is considerably simplified. All we had : ato do under these circumnstances was to 0include the rest of the tissue betweendouble ligatures, to sever between the o oligatures, to clear the artery and veiD,and sever all the nerves accompanyingthem, and even to tear away the ad-ventitia from their coats so as to be

42 0sure that the nervous connection wasclltthrough. We give in Fig. 11 a c Dr

tracing illtistrating the well marked X.X Xrhythm which is seen under these 4 ecircumstances and which is unaccom- 4ipatnied by any changes in the blood-pressure: many of the other subsequenttracings have been taken under like conditions.

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In all these cases we subsequently cut out the connecting portionsof artery and vein, hardened and cut sections of them, and submittedthe sections to microscopical examination; and the only nerve fibresthat could be seen in most of these instances were minute nerveslying actually in the thickness of the coats of the vessels. There was,however, one exception in which we had obtained experimental resultswhich appeared to indicate that we had failed to entirely accomplish ourobject of severing all nervous connection. On making a microscopicalexamination of the artery and vein in this instance we discovered aminute nerve lying between the artery and vein which was no doubt thecause of our obtaining a contrary result to that got from other experi-ments. For we had found that stimulation of the splanchnic nerve in thisanimal instead of producing, as in other cases where the nerves weresevered, an expansion ofthe spleen (Fig. 5) due to the rise ofblood-pressureconsequent upon the contraction of the abdominal blood vessels, causedwith a short preliminary expansion a marked contraction of the organ(Fig. 4), a contraction almost as marked as if all the nerves to the organhad been left. We conclude, therefore, that the nerves in the interiorof the organ must be very closely interdependent, since nervous impulsesconveyed through so small a number of nerve fibres as were containedwithin this small twig, were still able to produce a strong contraction ofthe organ.

In order to obviate any doubt as to the rhythmic movementsbeing carried on independently of the central nervous svstem weproceeded, in an animal in which the blood had been deprived of itscoagulability by the injection of peptone, to investigate the conditionsof rbythmic contraction of the organ when it was connected with thegeneral circulation simply through a glass tube tied in the artery. Wefound that even under these conditions the splenic rhythm was quiteobvious (Fig. 12) although in the small number of experiments whichwe succeeded in performing satisfactorily, the extent of the contrac-tion was much diminished. This however may probably be explainedby the depressing effect which peptonised blood produces upon all theinvoluntary muscular tissues of the body, and amongst them upon thetissue of the spleen.

Finally we have obtained rhythmic contraction and dilatation of thespleen in an excised organ contained within a spleen-box and suppliedwith the defibrinated and oxygenated blood of the same animal by themethod of perfusion at constant pressure. The vertical extent of thespontaneous contractions which we have obtained under these circum-stances is only small, nevertheless it is quite obvious. If, however, the

20


activity of the movements be increased by temporarily stopping theflow of blood through the organ, thereby producing in it an asphyxialcondition, the spleen curves become very marked indeed. This is shownin the tracing reproduced in Fig. 13.

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The larger curves of slow rhythm (about 1 per minute) which areobtained thus from the excised and perfused spleen may be beset with


smaller curves of a quicker and less regular rhythm the meaning ofwhich we are by no means clear about (Fig. 1.4 A and 14 B). They maycontinue to appear for as long as 3 hours or more after the excisionof the organ, in fact long after the regular slow rhythmic contractionshave ceased to show themselves.

FiG. 14A.

FIG. 14B.

The nerves of such an excised perfused organ remain irritable forsome time after excision and the inhibitory longer than the motor fibres.This fact is well illustrated in the two accompanying tracings (Fig. 14 Aand Fig. 14B) which are taken from the spleen of a dog which was excisedand perfused at cotnstant pressure with warmed oxygenated defibrinated

22


dog's blood. Stimnulation of the bundle of nerves accompanying theprincipal artery about 30 minutes after excision produced the effect ofcontraction of the organ which is shown in Fig. 14 A, whereas stimultationof the same inerves 24 hours later caused no contraction but a markeddilatation (Fig. 14 B).

The effect of drutgs upon the movements of the spleen.

It is stated by Roy that any slight alteration in the condition of theblood, whether produced by the injection of drugs such as curare ormerely by the addition of a small quantity of salt solution, will alwaysconsiderably increase the extent of the rhythmic movement. Theresults which we have obtained show that this statement is too genieral:that the increase of rhythmic movement which is obtained by varioussubstances is specific, and is not produced by injection of salinesolution alone. That the injection of a large amount of cold salinesolution into the veins will not produce any marked effect we are tiotprepared to state; but certainly the injection of a few centimetres ofnormal saline whether warm or cold produces no perceptible effect uponthe organ. On the other hand very minute doses of certain drugs andanimal extracts causes an extraordinarily marked effect upon therhythmic movements and this whether the drug or extract in questioninfluences the blood-pressure perceptibly or not.

One of the drugs which we have found to produce the most markedresult is that which is also mentioned by Roy, namely curare. Even inan animal which is already curarised to the extent of completely para-lysing the movements of the voluntary muscles, a very small additionaldose of curare will produce a marked increase in the splenic rhythm(Fig. 15) and this both with the nerves intact or witth the nerves cutor even with a glass tuibe connection of the organ in a peptonizedanimal (Fig. 16). This increase in the rhythm is still more marked,as might be supposed, when the animiial has not been previouslycurarised. A dose which will produce no perceptible effect upon thevoluntary nmuscles will cause a great increase in the extent of therhythmic movement in the spleen, which may last for some minutes.This result is obtained whether the curare causes, as has usually beeiithe case with that employed by us, a fall of blood-pressure, or, as insome instances which we have obtained, a rise.

The effect of extract of suprarenal upon the spleen was investigatedby one of us in connection with Oliver'; and it was shown that

I This Journal, xviii. 1895.

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suprarenal has the effect of causing an enormouis contraction, which maybe due to its direct action upon the blood vessels, or may be complicatedby an action upon the splenic muscular tisstue. We have obtained thesame result (Fig. 17) with the addition that the after effect of theinjection is to increase the extent of the normal rbythmic movementsof the organ. We have also found that a very strong contraction isobtained by direct injection of suprarenal extract even in minute dosesinto the artery of an excised and perfused spleen, thereby showingconclusively, as indeed had been sufficiently shown by Oliver and.Schiifer in the paper referred to, that the action of this drug isperipheral.

Of other animal extracts that which produces the most marked effectupon the spleen is extract of dried brain substance made with boiling wateror saline solution. Such an extract injected even in very small quantityinto the veins of the animal produces an enormous increase in the extentof the rhythmic splenic movements (Fig. 18 A and B). The injection ofthe extract is usually followed by a fall in the blood-pressure. This,however, very quickly resumes its normal height, anid may be followedby slight fluctuations in blood-pressure (increased Traube-Heringcurves ?). These are not synchronous with, nor in any way related tothe fluictuations in the splenic rhythm, and they may be altogetherabsent; the only result which is then seen is the marked effect uponthe spleen. The effect is seen also after all the nerves to the organare severed (Fig. 19).

Whereas extract of cerebral substance usually produces along withits effect upon the spleen a distinct fall of blood-pressure, extract ofthe pituitary body, as was shown by Oliver and Schiifer, causes amarked rise of pressure second only in extent to the rise which isproduced by injection of suprarenal. Nevertheless the effect upon thespleen is the samie as that of brain extract, namely a marked increasein the normal rhythmic movements.

Fig. 20 exhibits the results obtained from extracts made with boilingwater from the submaxillary gland, and the parotid gland of the dog.In each case the curve is almost exactly sitnilar. There is a fall ofblood-pressure followed by a gradual return to the normal with aslight after-rise. The effect upon the spleen is peculiar. There is atfirst a contraction of the organ followed by a temporary expansion whichdoes not however bring the organ back to the normal volume, and thisagain is followed by a more pronounced contraction; and as this passesoff the rhythmic contractions are seen to be increased in extent. Whatthe active agent may be in these cases has yet to be determined.

26

COffTRACTILITY OF SPLEEN. 27

Almost any agency which causes contraction of the spleen produces asan after effect increase of the rhythmic movement. But to this it may

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be added that certain agencies which produce primary expansion of theorgan, may also be followed by an increase in rhythmic movement.This is shown with weak stimulation of the splanchnic (Fig. 6) and itis also shown in the action of some extracts. We hiave obtained somiie-

28 E. A. SCHAFER AND B. MOORE.

what similar results to those got from submaxillary and parotid withextracts of pancreas and of liver; while manv other animal tissues haveyielded no result. There can be no question that these effects arespecific, seeing that they are not obtained with even much larger dosesof certain glands and extracts, nor with normal saline solution.

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Efects of dyspncea and anemia.

It was sbown by Sabinsky and confirmed by Bulgak and Roythat the effect of dyspnoea is to produce under normal conditions amarked contraction of the spleen. This we have been able also to con-firm (Fig. 21).. Such a contraction was also obtained by Setschenoff1on injection of the blood of an asphyxiated animal into the splenicartery. Roy confesses himself unable to decide whether this contractionof the organ is due entirely to the effect upon the nerve centres or to adirect stimulating action (by the imperfectly oxygenated blood) uponthe muscular and nervous tissues of the organ. Our experiments haveenabled us to decide this point, for while we have found that, as pointedout by Roy, in the spleen with the nerves intact, a condition ofsuspended respiration produces a marked contraction of the organfollowed in every instance by an increase in the specific rhythm;when all the nervous connections to the spleen have been severed, theresult, in the first instance, at any rate, is contrary, viz. passiveexpansion of the organ caused by the rise of blood-pressure due todyspncea; this passive expansion being followed by very strongly markedrhythmic waves of contraction and expansion (Fig. 22), which last, ifthe asphyxia becomes complete, until the vitality of the tissue is pre-sumably diminished too much by the want of oxygen. Fig. 23 maybe taken as an illuistration of this. It is a complete asphyxia curve ofspleen volume and blood-pressure in a curarized animal with all nervousconnections of the organ severed.

Anything which causes a greatly diminished supply or an arrestof flow of blood to the spleen produces a sitnilar result to that caused bygeneral dyspncea or asphyxia. This is for example obtained both bycompression of the aorta at the level of the diaphragm and by compres-sion of the splenic arteries. It was, as already stated, insisted upon byRoy that compression of the aorta at the level of the diaphragm althoughproducing an enormous fall of blood-pressure in the abdominal arteries,nevertheless causes only slowly and imperfectly a diminution in the sizeof the spleen. Roy expressly states that he repeated this experimentupon several occasions, and always with the same result. We havebeen entirely unable to corroborate this statement, having invariablyfound that compression of the aorta at the level mentioned by Roycauses an instant diminution in volume of the spleen of precisely such a

1 Quoted from the Russian by Bulgak, loc. cit.

29

E. A. SCGHAFER AND B. MOORE.

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nature as is produced by a direct cutting off of all arterial supply to theorgan. This is shown in two tracings which we here give (Figs. 24 and25). In one of these the nerves to the organ were intact; in the otherthey were all severed. In boththe blood-pressure was beingtaken from a tube connectedwith the carotid, and there isnaturally a rise of blood-pres-sure shown in both instances.The contraction of the spleenis extremely manifest, and thatcontraction is followed by an 6

increase in the rhythmic move-ments. The same result is egot by compressing with aclip forceps the branch of thesplenic artery through whichin many of our experimentsthe spleen was alone connectedwith the body,and this whetherthe nerves accompanying theartery were severed or not(Figs. 26 and 27).

A similar result is got bycompressingf the splenic vein,except that, of course, theimmediate result of this com-pression is to produce a greatexpansion of the organ. The oafter effect, however, is similar,namely an increasein therhythmic movements of theorgan. We think that it is .highly probable that the in-crease of these movementswhich is caused by a temporaryblock to the circulation throughthe organ is really due to anincreased excitability of themuscular fibres pro(luced by dyspneea, for it is obvious that the cutting

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off or diminishing the blood supply will cut off or diminish the supplyof oxygen to the spleniic tissue. We have utilised this method ofexciting the rhythm of the organ to obtaining a more marked rhythmnfrom the excised organ perfused with defibrinated dog's blood (Fig. 13).

FIG. 24. Effect upon spleen-volume and carotid pressure of temporaryocclusion of aorta above diaphragm.

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On the connexions of the splenic nerves with the spinal cord.

So far as we have been able to ascertain Bulgak is the onlyprevious observer who has endeavoured to determine systematically thenervous connexions of the spleen with the spinal cord. As we havealready shown (p. 3) Bulgak came to the conclusion as the result ofhis experimnents that the spleen receives fibres from the anterior rootsof from the 3rd to the 10th dorsal nerves of the left side.

We have successfully investigated this point in five dogs. In eachcase the animal was anaesthetized, at first with chloroform, and after-wards with morphia injected subcutaneously. A very small dose ofatropia was given along with the morphia to antagonize the depressanteffects of thiat drug upon the cardiac rhythm. The animal was thencurarized-a mirnimal dose of curare being employed-and artificialrespiration was maintained by pumping warmed air into the lutngs atregular intervals. The animal was also kept upon a tin of warm waterto obviate the cooling which would otherwise result from the prolongedaneesthesia and curarization. The whole length of the spinal cord wasthen exposed in the thoracic and lumbar regions and the nerve-roots onboth sides from the second postcervical to the fifteenth posteervicalwere tied with cotton threads of varying colours and cut close to thedura mater. The spinal cord at this part was then entirely removedalong with the enclosing dura mater. The blood-pressure was recordedby a mercury manometer connected with the carotid artery, and thespleen volume by the spleen plethysmograph. It will be readilyunderstood that with so severe an operation the animals are liable tosuccumb by reason of himorrhage or from other causes; but with alittle practice the experiment is less difficult to carry out than mightappear. The nerve-roots were stimulated first on one side and then on theother in succession from above down with a fairly strong faradaic current.

The results which we obtained in the five experiments are asfollows:-In four out of the five a distinct contraction of the spleen wasgot on stimulation of all the roots on both sides from the 3rd post-cervical to the 14th postcervical inclusive. rThe sharpest and mostextensive contraction was obtained on stimulation of the 6th, 7th and8th postcervicals; a well-marked and fairly sharp contraction on stimu-lation of the 5th and of the 9th and 10th, and a slight contraction onstimulating the 3rd and 4th and the 11th, 12th, 13th and 14th. Innone of the experiments did excitation of the 2nd postcervical pair

37


produce any contraction of the spleen. In none did excitation of thelath postcervical produce any contraction of the spleen. In every caseas already stated a contraction of this organ was obtained from theactive nerve-roots of both sides, but with each pair the amount ofcontraction was ceteris paribus less on stimulation of the nerve-roots ofthe right side than of those of the left side.

The curves shown in Fia. 29 are selected from a long series oftracings obtained from one animal, as illustrating the relative effects ofstimulating one of the more active and one of the less active nerve-roots upon the two sides respectively. They are taken with a compara-tively large and therefore by no means delicate tambour. The durationof the excitation in each case is indicated by the signal.

In one out of the five experiments performed successfully upon dogsexcitation of certain of the nerve-roots which in the other cases produceda contraction of the spleen failed to produce the usual effect, a gap beingleft in the series. This gap comprised the 11th anid 12th posteervicalpairs on both sides and the 13th nerve on the right side. We have noreason to suppose that these nerves were injured in exposing the cord.All the other nerves from the 3rd to the 14th postcervical on both sidesproduced the normnal effect. We are unable to sugggest a cause for thevariation unless it be an individual peculiarity in the nerve distributionin this particular animal.

We have made several attempts to work out the nerve-outflow fromthe spinal cord to the spleen in the cat in the same way as we haddone in the dog. The difficulties are however much greater in theformer animal for whether owing to the severity of the necessaryoperation or to the fact that these animals are more profoundly in-fluenced by the drugs used to produce anawsthesia and immobilisation,we have onlv in a single instance, out of several attempts succeeded incarrying out in a manner satisfactory to ourselves the whole series ofoperations and excitations necessary. In this instance we obtainedprecisely the same result as that which we had got in the dogs, viz.contraction of the spleen caused by excitation of the nerve-roots on bothsides from the 3rd postcervical to the 14th postcervical inclusive, withmore marked effects on the left side than on the right and with themost marked results from the 5th to the 9th postcervical pairs.

So far as it goes therefore this one experiment establishes the samerule for the cat as for the dog and renders it probable that in bothanimals the spinal root-connexion of the spleen is extraordinarily ex-tensive, embracing fibres from very nearly the whole thoracic-lumbarsympathetic outflow.

38


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On the probable ganglion-cell connexions of the splenic nerve-fibres.

We have endeavoured by the method of Langley and Dickinson'to determine with the aid of intravenous injections of nicotine, thesituation of the nerve-cell connexions of the nerves which pass from thespinal nerve-roots to the spleen. Most of our experiments have beenperformed uipon dogs. The method employed has been as follows:-The animal having been anaesthetized and curarized as in the ex-periments just recorded a small piece of the spinal cord was exposed atabout the level of the 7th or 8th postcervical nerve-roots. One of theseroots on the left side was then tied and cut close to the dura mater andthe segment of cord exposed was removed. The right splanchnic wasnext exposed by cutting away portions of two or three of the lower-most ribs, the nerve being partially separated, tied and ctit above theligature. The spleen was then laid bare and placed in the spleen box;the nerve-fibres accompanying one of its principal arteries being exposedso that they could also be readily stimulated. A blood-pressure tracingwas taken at the same time as the spleen tracing. The effects uponthe spleen volumne and blood-pressure of stimulating severally thenerve-root, the splanchnic and the spleen-rnerves were recorded. Asmall dose, usually 1 mgr., of nicotine was then given by intravenousinjection and the above effects again recorded. This was repeated withsuccessive doses of 1 mgr. of nicotine until about 5 mgrs. of nicotine hadbeen given in all. An additional dose of 10 mgrs. was then given andthe excitations were repeated; and again after a final dose of another10 mgrs., making about 25 mars. in all for a dog weighing about 7 kilos.

The results of these experiments have been quite uniform. Theyshow that with successive smnall doses of nicotine up to 5 mgrs. the effectof stimulating the nerve-root becomes less and less until with a dose ofa mgrs. for a moderate sized dog it has entirely disappeared, whereasthe effects of stimulating the splanchnic and the spleen nerves are notperceptiblv abated. But witlh the larger doses the effects of stimulatingboth the splanchnics and the spleen nerves are greatly diminished; thediminution being proportionately greater for the splanchnic than forthe spleen nerves, but very evident in the latter nevertheless. Wehave performed a single successful experiment upon the cat, withsimilar results, and of this experiment we give the chief tracinos inFigs. 30, A, B, Cand D. But most of our experiments on this animal with

1 Pr-oc. Roy. Soc. XLVI. 1889 and XLVII. 1890; This Journal, xi. 1890.

40


FIG. 30 A. Cat, 2-75 kilos. Atropia (2 mgr.), curare, artificial respiration. The animalwas anlesthetized with chloroform for the necessary operations.

This tracing shows the marked contraction of the spleen resulting from excitationof the 5th postcervical nerve root on the left side after 2 mgr. only of nicotine had beenadministered. Stimulation of the cut right splanchnic and of the spleen-nerves gaveprecisely similar results. The blood-pressure tracing has not been reproduced: itshowed a well-marked rise on stimulation of the root.

FIG. 30 B. Continuation of the experiment, another milligram of nicotine having now been adminis-tered, making in all 3 mgr. The effect upon the spleen and blood-pressure of stimulating the nerve-root is completely abolished, whereas the effect of stimulating the splanchnics and spleen-nervesis little if at all diminished.


nicotine have been unsuccessful, partly for the reasons previously giveu(p. 38), partly because in nearly all cases the result of injectingnicotine in the cat has been to leave the spleen so strongly andpermanently contracted that it was rendered useless for further ex-perimentation.

From the above effect of small doses of nicotine, obtained in severaldogs and in one cat, we felt that we were justified in concluding thatthere is a cell-station for the splenic nerves between the nerve-rootsand the splancbnic and therefore in the ganglia of the sympatheticchain; while the effect of large doses appeared to show, although not so

FIG. 30 C. Continuation of previous tracing. Effect of stimulating peripheral spleen-nervesafter 3 mgr. nicotine.

con3clusively, that there is another cell-station less readily blocked by nico-tine, between the splanchnics and the nerves accompanyiing the splenicvessels and therefore presumably in the semilunar ganglion. But on

42


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the reading of our preliminary communication before the Royal Society'it was suggested by Dr Langley that the abolition of the nerve-rooteffect after a small dose of nicotine might be due to the fact that thereare relatively few fibres in one nerve-root, and that assuming thatnicotin even in small doses tends to produce a certain amount of paralysisof the spleen nerves, this would show itself sooner for the few fibres inthe root than for the many fibres in the splanchnic. To this it might bereplied that we have also only stimulated a few fibres in the peripheralnerves accompanying the branch of the splenic artery and have still gotafter comparatively large doses of nicotine a well-marked contractionof the spleen. Moreover as we have already shown, a minute nerve-twigcontaining a very few fibres indeed, may convey nervous impulses suf-ficient to produce a very strong contraction of the organ (Fig. 12).

And further it may be pointed out that althotugh nerve-fibres passto the spleen from very many nerve-roots it is nevertheless probablethat the ordinary course of nervous impulses to the organ is along thefew roots stimulation of which is found to produce the sbarpest andmost marked contraction, since these present in all probability theleast resistance to the passage of such impulses. These few roots arein the dog the 6th, 7th and 8th of the left side. Stimulation of anyone of these may produce nearly or quiite as great a contraction of thespleen as stimulation of the greater splanchnic of the right side, whichis the one used in our experiments. We think therefore that theresults obtained by stimulating one of these left roots and the rightsplfanchnic before and after a small dose of nicotine are quite comparable;and that the block which such a dose of nicotine produces can only beput down to an effect upon a cell-station in the ganglionic chain.

Nevertheless in order to obtain a stimulation of the fibres not ofone root only but of several or all the roots on the left side we havevaried the experiment in the following manner: -Having laid bare thewhole lenigth of the dorsal cord in an anesthetized and curarizedanimal (dog weighing 7 kilos) we cut throuigh the cord at about thelevel of the 3rd dorsal vertebra, taking care that there was a consider-able gap left between the upper and lower cut ends. We then placedone guarded needle electrode in the upper end of the severed portionof the cord and another at the level of the 10th dorsal nerves so thatwe could send a strong faradaic excitation through almost the wholelebgth of the thoracic cord, and therefore also through the origins ofall the anterior nerve-roots. The splanchnic was exposed and cut onthe right side as before and placed on another pair of. electrodes to

1 Proc. Roy. Soc. Feb. 1896.

44

CONTRA CTILITY OF SPLEEN.

which the same excitation as was used for the cord could be switched onat any momnent. The results of this experiment are shown in the accom-panying tracings (Figs. 31 A, B and C). Excitation of the cord, of thesplanchnic, and of the spleen-nerves each produced in the first instancea sharp and powerful contraction of the spleen. These were all alikeand simnilar to the splanchnic effect shown in Fig. 31 A; we havenot therefore thought it necessary to reproduce them. Nicotine wasthen given in successive doses of 1 ingr. The first obvious effect wasproduced after 3 mngr. had been admninistered. The contraction resultingfrom the cord-excitation was diminished; whereas the splanchnic andspleen nerves still have an undiminished effect. After another mgr. ofnicotine the cord effect is hardly perceptible (Fig. 31 A); the other effectsare both quite strong'. After injection of another mgr. (5 rngr. in all)the contraction resulting from the cord-excitation was entirely abolished(Fig. 31 B) while the splanchnic and spleen nerves still give a powerfulresult. Another 5 mgr. (i.e. 10 mgr. in all) produced no alteration inthis result. As in the other experiments (upon the single nerve roots)it now requires a large dose of nicotine (20 mgr. more or 30 mgr. inall) materially to affect the splanchnic and peripheral nerves. Andalthough the effect of the nicotine is most marked upon the splanchnic,nevertheless the contraction which results from stimulating this nerveis not altogether abolished even by 30 mgr. of nicotine, while thatwhich results from stimulating the nerves accompanying the splenicartery is also markedly diminished (Fig. 31 C).

We also reproduce a tracing obtained from the cat under similarconditions but prior to the administration of nicotine (Fig. 32). The ex-periment was incomplete, for the results of stimulation could not berecorded after the administration of nicotine on account of the persistentcontraction of the spleen caused by that drug in this particular animal.But the curves are instructive as showing the similarity of effectproduced by stimulating respectively the severed dorsal cord, the cutright splanchnic and the spleen nerves. In this case the greatestamount of contraction was obtained from the cord and the least fromthe spleen-nerves. The contraction persists long after the stimulationhas ceased an(d is followed by increased spleen-waves. Stimulationl ofthe cord and of the splanchnic is accompanied by rise of blood-pressure,which is not seen on stimulation of the spleen-nerves. This rise ofblood-pressuire is abolished (as mav be seen in Fia. 30 D) by the samedose of nicotine as suffices to abolish the spleen-contraction.

1 Only the cord effect and the splanchnic effect are shown in the tracing: the spleen-nerve efTect was exactly like that obtained from the splauchnic,

45

E. A. SCHAFER AND B. MOORE.46


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CONCLUSIONS.

The general results of our experiments may be thus summarised.1. The rhythmic contractility of the spleen is inherent, and may

be carried out entirely independently of the central nervous system orof the large sympathetic ganglia.

2. The spleen receives both motor and inhibitory fibres throughthe splanchnic nerves.

3. The pneumogastric nerves contain no fibres which directlyinflueince the contraction of the organ.

4. The spleen volume is extremely responsive to all fluctuations inthe general blood-pressure, and the circulation through the organ canbe and probably is entirely brought about, as in other organs, by thedifference between arterial and venous pressure.

5. The spleen contractility is very responsive to dyspnoic conditionsof the blood, these producing not only a general contraction of theorgan but also an increase in the extent of its rhythmic movement.When, however, the nervous connections of the organ are severed,primary expansion of the spleen is obtained in asphyxia, a passiveresult of the rise of general blood-pressure.

6. Certain drugs and extracts have a specific action in increasingthe extent of the rhythmic movements of the spleen. Amongst thesemay be mentioned as having a marked effect curare and brain extract.

7. The muscular tissue of the spleen in the dog and cat isinnervated through an extraordinarily large number of nerve-roots, viz.from the third postcervical to the fourteenth postcervical inclusive.

8. The largest outflow of nerve fibres, if we may judge by theamount of contraction produced, occurs from the fifth postcervical tothe ninth postcervical inclusive.

9. Reasoning in the same way, the outflow is in each pair of nerve-roots larger upon the left than upon the right side, i.e. it is not bilaterallysymmetrical.

10. Judging from the effects produced by intravenous injectionsof nicotine, the outflowing fibres probably have a cell-connection inthe main ganglionic chain of the sympathetic, and perhaps anotherin the semilunar ganglion.

50

on the contractility and innervation of the spleen

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