Oscillation of Blood Flow andVascular Resistance

During Mayer Waves

By Thomas Killip, III, M.D.

• In experimental animals in poor condition,slow spontaneous oscillations in blood pressuremay often be observed (fig. 1). Termed Mayerwaves,* after the description by SiginundMayer in 1876/ they are slower than the re-spiratory rate.2 Small Mayer waves oftendevelop in animals bled to an arterial pres-sure between 60 and 80 mm. Hg. Bilateral

From the Department of Medicine, The NewYork Hospital-Cornell Medical Center, New York,New York.

Supported by National Heart Institute GrantH-6633 to Professor B. Uvniis.

This work was performed during a Special BesearchFellowship from the National Heart Institute in thelaboratory of Professor Uvniis, Department of Phar-macology, Karolinska Institutet, Stockholm.

Beceived for publication July 5, 1962.*The eponyms Traube-Hering and Mayer have been

applied both disparately and synonymously. Traube3

describod a rise in arterial pressure, followed byslow oscillations at a frequency of seven per minute,when artificial respiration was halted in the curarized,vagotomized dog. After two or three minutes ofrespiratory arrest, blood pressure fell, and the wavesceasod. Hering1 noted the same phenomenon in thedog and the cat under similar experimental condi-tions. Traube and Hering postulated that the waveswero due to rhythmic activity of the vasomotorcentor acting under the influence of strong respira-tory center discharge attempting to overcome therespiratory arrest. If this interpretation is correct,then Traube-Hering wavos would be synchronous withrespiration when observed during spontaneous breath-ing. Mayer1 described blood pres»ure waves in nar-cotized rabbits, cats, and dogs with low bloodpressure and in poor condition. He stated that thewaves wero slower than the respiratory rate. Becauseof the generality of Mayor's description, the termMayer waves is used for the blood pressure oscilla-tions discussed in the present paper. Traube-Heringwaves are more restricted by definition, and it seemsreasonable to apply the term to experimental circum-stances duplicating those originally described byTnuibe and Hering. Possibly, Mayer waves andTraube-Hering waves have a similar physiologicalbasis, but this remains to be proved.

Circulation Research, Volume XI, December 1961

carotid clipping will usually exaggerate thepressure rise which may reach an amplitudeof 80 mm. Hg or more with each wave.5 Va-gotomy reduces the amplitude of the waves,as does breathing pure oxygen. They areabolished by sinus nerve block, inactivationof the carotid chemoreceptors, or sympatheticblockade.5' °

It has long been postulated that Mayerwaves are due to rhythmic change in vaso-motor function,1' 2< B> ° but evidence to supportthis thesis has been scant. The experimentsdescribed herein were designed to determinewhether Mayer waves are accompanied by anoscillation of vascular resistance. Blood flowwas measured in different vascular beds andthe changes in resistance calculated. The dataindicate that Mayer waves are accompaniedby rhythmic fluctuations in vascular resist-ance which vary regionally.

MethodsExperiments .vere performed on cuts anesthe-

tized with chloralose intravenously (60 to 80mm./Kg.) and tracheotomized. Heart rate wasrecorded with an interval recorder.7 Blood flowswere measured with a drop flow meter.8 Vesselswere cannulated with polyethylene tubing and theanimal heparinized. The drop chamber and tubingwere enclosed in a water jacket maintained at 38 C.The rate of formation of drops was recorded byan ordinate writer connected to a polygraph. Theordinate writer is so constructed that the heightof rise of the marking pen is inversely proportionalto the flow rate. Thus, when perfusion pressure isheld constant, the rise of the marking pen is di-rectly related to the resistance to blood flow in theregion being perfused.

For measuring flow in the great vessels, the ab-dominal aorta and inferior vena cava were ap-proached retroperitoneally through a flank incisionand winnulated just caudal to the renal vessels.Venous pressure in the inferior vena cava was heldconstant, between 3 and 6 mm. Hg, by allowingblood from the venous flow meter to drip from a

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Aim RIALPMS8UM

FIGURE 1

Mayer waves and oscillation of respiration. Arte-rial pressure fluctuates 50 mm. Hg at a frequencyof 3.6 per minute. Note that cyclical changes inrespiration slightly precede those of blood pres-sure.

fixed height into n funnel draining into the tho-racic vena cava.

Arterial inflow was measured in muscle, skin,kidney, and small intestine. In all experiments,flow in muscle was measured simultaneously withat least one other organ flow. In a few experi-ments, all four flows were determined simultane-ously. A hind leg was skinned with electrocautery,circulation to the paw occluded with a tight liga-ture above the ankle, and the femoral or iliacartery cannulated for muscle flow. Mow to skinwas measured via cannulation of the dorsal veinor artery of the paw. When the vein was utilized,collateral veins draining the paw were ligated. Nodifference in results was apparent between use ofthe artery or vein. For renal flow, the renal arterywas cannulated after carefully dissecting away therenal nerves. A large mesenteric artery servingthe ileuin was chosen for measuring gut inflow andthe nerves dissected from the vessel.

In order to maintain a constant perfusion pres-sure to the organs in which flow was being re-corded, despite large changes in systemic pressure,the inflow side of the drop chamber was connectedto a special stopcock which in turn received ar-terial blood from the iliac or femoral artery oppo-site the skinned leg. The stopcock had multipleoutlets which allowed measurement of arterial pres-sure proximal (systemic) and distal (perfnsion)to a variable occluding screw and which permittedsimultaneous perfusion of four drop chambers attho same pressure. Arterial pressures were meas-ured with Statham strain gauges. Respiration wasrecorded from intratraeheal or right atrial pressure.

Initially, Mayer waves were produced by re-peated hemorrhage and transfusion. In not everyanimal, however, were the waves of sufficient am-plitude to permit iinnlysis of the records. It wasthen found that a combination of hemorrhage andgraded carotid occlusion reliably resulted in Mayer

„«. H 1 1 1 1 1 1 1 1 ( 1 1 ±

FIGURE 2

Flow in abdominal aorta> and vena cava duringMayer waves. Respiratory cycles are reflected inright atrial pressure curve. Aortic flow varies in-versely with systemic pressure. Vena caval flmcchange lags four to six seconds behind aortic.

waves of 40 mm. Hg or more amplitude. In thelater experiments, both common carotids wereperfused from an arterial source via a secondvariable stopcock. After hemorrhage sufficient tolower the arterial blood pressure below 80 to 100mm. Hg, setting the screw clamp somewhere be-tween partial and complete closure was followedby the development of large and usually per-sistent Mayer waves. When the carotid screwclamp was opened, permitting normal flow, thewaves disappeared.

ResultsSuccessful experiments with the develop-

ment of Mayer waves of large amplitude wereachieved in 17 cats (fig. 1). The averageMayer wave was 56 mm. Hg in amplitude(range 25 to 105 mm.) developing from abase systemic pressure of 70 mm. Hg (range45 to 100 mm.), with a frequency of 3.0/min.(range 1.6 to 4.3/min.). There was no correla-tion between amplitude and frequency orbetween base systemic pressure and ampli-tude. When the waves were small, minoradjustment of blood volume by bleeding ortransfusing a few ml. of blood frequently re-sulted in a striking increase in amplitude.Partial carotid occlusion had a similar effect.

Mayer waves were invariably accompaniedbj' cyclical variations in respiration in spon-taneously breathing animals (figs. 1 and 2).The respiratory cycles varied with the samefrequency as the Mayer waves, althoughslightly out of phase. The maximum depth

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BLOOD FLOW DUEINO MATER WAVES 989

PUOHT XTDIAL

wm Hf

ARTERIALPRESSURE

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2001

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FIGURI 3Mayer waves wrtd aortic flow during constant aorticperfusion pressure. Note oscillation of flow andpressure. Striking decrease in flow reflects markedincrease in vascular resistance with each arterialpressure icave.

of respiration preceded by a few seconds peakarterial pressure. Minimal respiratory excur-sions occurred slightly before the trough ofthe systemic pressure. Cyclical variations inthe respiratory rate were also noted. On sev-eral occasions, Cheyne-Stokes breathing de-veloped (fig. 2).

In three animals, Mayer waves were ob-served both during spontaneous ventilationand during positive pressure ventilation withroom air at a constant rate and tidal volumeadjusted to suppress spontaneous ventilation.There was no apparent difference in theblood pressure waves in the two differenttypes of respiration.

The ventricular rate was monitored in 12experiments. In ] 1 animals with Mayer waves,there was no change in heart rate during thepressure oscillations. Heart rate varied from150 to 254, averaging 214/min. In one animal,heart rate decreased duriug the pressure riseby 8 per cent, falling from 215 to 198 beats/min.

Flow was meHSured simultaneously in theabdominal aorta and inferior vena cava inseven animals. With Mayer waves of largeamplitude, flow in the aorta and vena cavavaried inversely with the arterial pressure(fig. 2). The oscillation of flow in the vena

Circulation Research, Volumo XI, Decembor 196B

MUSCLE FLOWml/mln

INTESTINALFLOW

ml/mln

RENAL FLOWml/mln

SKIN FLOWml/mln

TIME10 tee H+H+H

FIGURE 4

Regional blood flotv during Stayer waves. As arte-rial pressure rises, muscle (Mid intestinal flow de-crease, whereas renal and cutaneous flow increase.

cava lagged four to six seconds behind that inthe aorta. The effect of this lag was to providea surge of venous return as the systemic pres-sure was declining and just preceding thepressure rise of the next Mayer wave. Byvarying aortic perf usion pressure with a screwclamp when systemic pressure was constantand no Mayer waves were present, it waspossible to produce continuous fluctuationsin aortic flow similar to the flow change ac-companying Mayer waves. Under these cir-cumstances also, caval flow lagged four to sixseconds behind aortic flow. This observationsuggests that the lag is related to the circula-tion time between points of measurement ofaortic and venous flow.

The fluctuations in arterial pressure wereassociated with a parallel rise and fall incalculated vascular resistance during con-stant perfusion pressure in the lower half ofthe body (fig. 3). In four experiments with

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FIOURE 3

Begional vascular resistance during Mayer waves-Data averaged from experiments in which regionalblood flow was measured during constant perfus-ionpressure. See text for details. Ordinates: pressureill mm. Hg and resistance in units. Note hierarchyof resistance change in muscle, intestine, skin, andno resistance change in kidney.

Mayer waves averaging 60 mm. Hg (range45 to 65 nun. Hg), resistance in the hind-quarters averaged a 230 per cent increase(range 160 per cent to 282 per cent) as thepressure rose. Any procedure which abolishedthe waves, such as transfusion or excessivebleeding, cutting the vagi, or reducing thedegree of carotid occlusion also abolished theresistance oscillation. Rhythmic fluctuationsin resistance were observed only in the pres-ence of Mayer waves.

The pattern of blood flow during Mayerwaves varied in the four regions investigated(fig. 4). With Mayer waves of large ampli-tude, muscle blood flow decreased during the

pressure rise and increased during the pres-sure fall. Blood flow in the small intestineshowed a similar response, but the changeswere less pronounced. Skin blood flow usuallyincreased modestly during the pressure rise.Renal blood flow was markedly sensitive andvaried directly with the arterial pressure.

Regional vasoconstrictor responses duringMa}rer waves were compared quantitativelywith constant perfvision pressure (fig. 5).Muscle vascular resistance increased in 12 ex-periments, an average of 276 per cent (range206 per cent to 440 per cent) from trough topressure peak. Vascular resistance in smallintestine increased an average of 210 per centin four experiments (range 179 per cent to280 per cent). Skin resistance increased 136per cent in five animals (range 112 per centto 199 per cent). Kidney showed no changein resistance. In none of eight experimentswas there any evidence of renal vasoconstric-tion during Mayer waves.

Because of the possibility that nerve dam-age accounted for the observed differences invascular resistance, the nerves accompanyingthe intestinal and renal artery were stimu-lated at the end of each experiment at fre-quencies ranging from 1 to 16 per second.One or two nerves accompanying the arterywere selected, divided, and the distal end stim-ulated. In every case, stimulation at low fre-quency produced vasoconstriction in the gutor kidnej'. Frequency response curves had theclassical form but were shifted to the rightsince only a few of the nerves to the organwere being stimulated. Stimulation in the re-gion of the celiac ganglion also producedrenal vasoconstriction.

In three experiments in which blood flowhad been measured during Mayer waves, theeffect of asphyxia was observed. Perfusionpressure was held constant during trachealocclusion, although systemic blood pressurerose considerably. During asphyxia there wasmarked vasoeonstrietion in the muscle, gut,and skin, as well as kidney. The constrictorresponse during asphyxia is interpreted asfurther evidence that the innervation to theorgans studied was intact.

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DiscussionThe present study has shown that Mayer

waves are accompanied by cyclical variationsin respiratory movements, blood flow, and re-sistance to blood flow, but no change in heartrate. Possible limitations of the experimentaltechniques merit discussion. The anesthesiamay have influenced the results. Chloralosehas been shown to reduce baroreceptor func-tion and alter the effect of sinus nerve stimu-lation in the cat.0 With another agent or inthe unanesthetized animal, a different patternof cardiovascular response with Mayer wavesmay occur.

Measurement of blood flow required dissec-tion and cannulation of the artery supplyingblood to the region under study. Less than10 per cent of the sympathetic vasoconstrictoractivity in thigh muscle is interrupted by li-gation of the femoral artery.10 What fractionof the constrictor fibers is in the adventitia ofarteries to skin, kidney, and gut is not known.The nerves of the kidney and gut are inti-mately related to their respective arteries, andundoubtedly some were damaged during theinsertion of the cannula. However, since stim-ulation of the nerves to the kidneys and gutproduced striking vasoconstriction at thetermination of the experiments, and sinceasphyxia caused extreme vasoconstriction inall vascular beds cannulated, it is unlikelythat nerve damage adversely affected the re-sults.

Maintenance of a constant perfusion pres-sure lowered mean blood flow and exaggeratedthe decrease in regional flow as vascular re-sistance increased during Mayer waves. Theadded resistance of the screw clamp accentu-ated the systemic pressure rise and fall. Thesealterations may have influenced the observedfluctuations in flow and resistance. The de-creased flow might have produced sufficientlocal metabolic change to cause a vasodilation,similar to reactive hyperemia, thus distortingthe actual resistance change. The increasedamplitude of the waves might have alteredthe distribution of blood flow. To minimizethese possibilities, constant perfusion pressurewas limited to the vascular bed under study.

Circulation Rcsaarck, Volume XI, December 1961

Comparison of records obtained with bothconstant perfusion pressure and systemic per-fusion pressure revealed similar oscillationsin calculated resistance. It is considered un-likely, therefore, that the constant local per-fusion pressure significantly affected the ex-perimental results.

Mayer waves appear to be reflex in origin.11

Andersson et al. eliminated them in cats bysinus nerve section or selective destruction ofthe chemoreceptors.5 They postulated thatMayer waves are the result of an oscillationbetween baroreceptor and chemoreeeptor func-tions. Guyton et al. demonstrated that epi-dural sympathetic blockade or pressoreceptordenervation obliterate Mayer waves in thedog.6 They also proposed an oscillation be-tween the pressoreceptors and autonomic re-flex vasoconstriction as an explanation.

The failure of heart rate to change duringMayer waves is of interest since baroreceptorstimulation during the pressure rise would beexpected to cause bradycardia. In the cat, thetachycardia of systemic anoxia is unaffectedby changes in the oxygen content of carotidbody perfusate,12 although stimulation of thechemoreceptors by cyanide causes a promptincrease in heart rate.13 Since chloralose de-presses baroreceptor function in the cat,0 theconstant heart rate observed in the presentexperiments suggests that the baroreceptorsare less important in the genesis of Mayerwaves than has been proposed. Followingcerebral compression or increased cerebralspinal fluid pressure, large Mayer waves de-velop which are unaffected by carotid andaortic denervation.14 A direct role for thevasoconstrictor center or some other area inthe brain in the genesis of Mayer waves can-not be ruled out.

The cyclical variation in respiratory depthand rate in the spontaneously breathing ani-mals may be a reflection of the rhythmicchemoreceptor discharge known to accompanyMayer waves.16 That the respiratory variationis not necessary for the blood pressure oscilla-tions is shown by their occurrence duringconstant positive pressure ventilation. Therespiratory cycles slightly precede the blood

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pressure waves, as does the increase in theintensity of discharge of the chemoreceptornerves.11 This suggests that the ventilatorymechanism reacts faster to a common stimulusthan does the vascular system.

Whether oscillation of vascular resistance isthe only factor controlling the pulse pressureof Mayer waves cannot be determined fromthe present data since cardiac function wasnot measured. It is possible that rhythmicalteration of myocardial contractility and car-diac output may contribute. If venous returnto the right heart lags behind the arterialpressure fluctuation, as was true for flow inthe inferior vena cava, then a changing car-diac output might either augment or depressthe pressure rise, depending on the frequencyof the waves and the degree of lag.

Few data comparing vasoconstriction in twoor more regions to the same afferent stimulusare available. Rein found that during carotidocclusion, muscle had the most active reflexvasoconstriction and kidney the least, whilegut was intermediate.10 Bern thai and Sehwindshowed more intense vasoconstriction in mus-cle and skin than in the gut during carotidbody stimulation.17 McGiff and Aviado haverecently reported that anoxia and carotid oc-clusion have a greater effect on femoral thanon renal vascular resistance.18 In the cat, bul-l>ar stimulation is associated with more intensevasoconstriction in muscle than in skin orkidney.10

Measurement of regional blood flow andresistance during Mayer waves has providedan opportunity to observe dynamic changesduring a fluctuating central stimulus of pre-sumably constant peak intensity. Since theevidence indicates that Mayer waves are reflexin origin, the varying pattern of vascular re-sistance may be interpreted as indirect evi-dence for inherent regional differences in thecentral control of the peripheral vascular sys-tem. The greater vasoconstrictor activity ofmuscle and gut confirms the experience ofother workers. Failure to demonstrate renalvasoconstriction during Mayer Avaves is ofinterest in view of the long-standing debate

about the role of the kidney in reflex bloodflow distribution.

The ultimate vasoconstrictor response to acentral stimulus must depend upon an inter-action between local and central mechanisms.As the animals were bled and arterial pres-sure fell, blood flows fell to very low values(fig. 4). What role local factors, perhaps in-fluenced by anerobic metabolism, may play inrelation to central stimuli in the regional flowand resistance changes observed in Mayerwaves cannot be determined from the presentdata.

SummaryIn cats anesthetized with chloralose, Mayer

waves developed following graded hemorrhageand, in some, partial carotid occlusion. Theaverage Mayer wave was 56 mm. Hg in ampli-tude rising from a base systemic pressure of70 mm. Hg at a frequency of 3.0 per minute.Rhythmic fluctuation of respiratory depthand frequency paralleled but slightly precededthe blood pressure change. There was no sig-nificant variation in heart rate during Mayerwaves.

Flow in the abdominal aorta and vena cavavaried inversely with systemic pressure. Aflow lag of four to six seconds in the vena cavabehind that in the aorta during Mayer waveswas probably related to circulation time.

Blood flow was measured in muscle, smallintestine, skin, and kidney. During the pres-sure rise of each Mayer wave, blood flow de-creased in muscle more than in gut. Cutaneousflow increased moderately. Renal flow varieddirectly with the arterial pressure. Changesin vascular resistance were evaluated by hold-ing perfusion pressure constant and measur-ing regional blood flow. During Mayer waves,muscle vascular resistance increased 276 percent, intestinal resistance increased 210 percent, and cutaneous resistance rose 136 percent. Renal vascular resistance did not change.

Since Mayer waves are apparently reflexo-genic in origin, the data are interpreted asevidence for regional differences in the pat-tern of central reflex control of the peripheralvascular system.

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AcknowledgmentThe author owes a debt of gratitude to Percy

Limlgren, M.D., and Professor Borje Uvniis for in-valuable support and advice. Lars Wallenberg providedhelpful assistance in many of the experiments.

AddendumSinco tliis paper was propared for publication, B.

Lofving (Cardiovascular adjustments induced fromthe rostral cingulato gyrus. Acta physiol. scandinav.53, suppl. 184, 1961) has published a fignre showingdocroased muscle blood flow and passive increasein renal blood flow during Mayer waves. He statesthat Mayer waves aJIectod the nervous tone of vesselsin skin tind gut to a lesser extent than in muscle.

References1. MATES, S.: Studien zur Physiologic des Herzens

und der Blutgefiisso: V. Uber spontane Blut-druckschwankuugen. S.-B. Akad. Wiss. Wien,math.-nat. B3. 74: 302, 1876.

2. SCHWEITZER, A.: Ehythmical fluctuations of thearterial blood pressure. J. Physiol. 104: 25P,1945.

3. TKAUBK, L.: TJober periodische Thiitigkeitg-Aeusserungen des vasomotorischen und Hem-mungs-Nerven Zentrums. Zentralbl. med. Wiss.66: 881, 1865.

4. HERING, E.: t)ber den Einfluss der Athmungauf den Kreislauf. S.-B. Akad. Wiss. Wien,math.-nat. K\. 60: 829, 1869.

5. ANDERSSON, B., KENNEY, B. A., AND NEIL, E.:

Bole of the chemoceptors of the carotid andaortic regions in the production of the Mayerwaves. Acta physiol. scandinav. 20: 203, 1950.

G. GUYTON, A. C, AND HARRIS, J. W.: Pressore-

coptor-autonoinic oscillation: A probable causeof vaaomotor waves. Am. J. Physiol. 165:158, 1961.

7. GOLDSOHMIDT, H., AND LiNDOEEN, P.: Electronicinterval recorder for measuring peripheralblood flow. J. Appl. Physiol. 17: 169, 1962.

8. LINDGREN, P.: Improved method for drop record-

ing of arterial or venous blood flow. Actaphysiol. scandinav. 42: 5, 1958.

9. NEIL, E., BEDWOOD, C. B. M., AND SCHWEITZER,

A.: Pressor responses to electrical stimulationof the carotid sinus nerve in cats. J. Physiol.109: 259, 1949.

10. CLONNINGER, G. L., AND GREEN, H. D.: Path-

ways taken by the sympathetic vasomotornerves from the sympathetic chain to thevasculature of the hind leg muscles of thedog. Am. J. Physiol. 181: 258, 1955.

11. HEYMANS, C, AND NEIL, E.: Beflexogenic Aroasof the Cardiovascular Systom. Boston, Little,Brown & Co., 1958.

12. NEIL, E.: Influence of the carotid chemoceptorreflexes on the heart rate in systemic anoxia.Arch. int. pharmacodyn. 106: 477, 1956.

13. LANDGREN, 8., AND NEIL, E.: Effect of chemicalstimulation of the carotid bodies on the heartrate of the cat. Acta physiol. scandinav. 26:286, 1952.

14. GUYTON, A. C, AND SATTERTIELD, J. H.: Vaso-

motor waves possibly resulting from CNSischemie reflex oscillation. Am. J. Physiol.170: 601, 1952.

15. NEIL, E.: Chemoceptors. In Control of the Circu-lation of the Blood. Supplementary volume,edited by E. J. S. McDowall. London, Wm.Dawson and Sons, Ltd., 1956.

16. BEIN, H.: Vasomotorische Begulationen. Ergeb.Physiol. 32: 28, 1931.

17. BERNTHAL, T., AND SOHWIND, P. J.: Comparison

in intestine and leg of the reflex vascular re-sponse to carotid-aortic chemoreceptor stimu-lation. Am. J. Physiol. 143: 361, 1945.

18. MOGIFF, J. C, AND AVIADO, D. M.: Differential

response of renal and femoral blood flows andvascular resistance. Circulation Besearch 9:1327, 1961.

19. KNAPP, F. M., AND LINDGREN, P.: Quantitative

aspects of bulbar control of the sympatheticvasoconstrictor nerves. Acta physiol. scandinav.60 (suppl. 175) : SS, 1960.

Book Review

Electron Microscopy of the Cardiovascular Sys-tem, Bruno Kisch. Springfield, Illinois, CharlesC Thomas, 1960, 180 pages, illustrated. $7.50.The following suggestions nre made on th,e bnsis

of observations under the electron microscope:(1) The location und ultramicroscopic structuresof the cardiac nerves suggest that axon reflexesare untenable; all branching of the finest nervefibers is a separation of pi'eforined individual pro-totixons, never n dividing of a common stem, nsrequired to mediate an axon reflex. (2) The abil-

CircvXation Research, Volume XI, December lOtt

ity of a muscle to do heavy work can be mathe-matically stated ns n function of the type ofsarcosomes found within its muscle fibers. (3)Muscle fibrils of cardiac muscle and the fibrils ofother types of striated muscle exhibit no basicdifferences. (4) The inner surfnce of the capillaryis scalloped, and long ribbon-like extensions fromthe endothelial wall may stretch deep into thebloodstream within the capillary lumen. The pic-tures and techniques for preparation of heartspecimens are included in this monograph.

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Thomas Killip IIIOscillation of Blood Flow and Vascular Resistance During Mayer Waves

Print ISSN: 0009-7330. Online ISSN: 1524-4571 Copyright © 1962 American Heart Association, Inc. All rights reserved.is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231Circulation Research

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