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to symptoms in adults. If the majority of infants at birthhave a folded epiglottis, at what age does this flatten out ?Necropsy records in children’s hospitals should providean answer.

J. B. CLELAND.The University, Adelaide,

South Australia.

A SEX-LINKED BLOOD-GROUP

ROBERT J. HETHERINGTON.Summerfield Hospital,

Birmingham, 18.

SIR,-Dr. Mann and his colleagues (Jan. 6) have placedus all in their debt.But why is Mr. And. described as

" Caucasian " ? Can it bethat pangenesis is still accepted at Grand Rapids ? More to thepoint, why was the rare antiserum wasted on a fruitless searchfor correlation with one of the thousands of parameters in theAmerican gene pool ? So far as anthropology is concerned,having once discovered the American frequency, which is

usually independent of skin pigment, the next step is to deter-mine the frequency in non-American populations. By suchresearches, which can be followed in the analyses of Mourant,lthe word " Caucasian " is losing even more meaning.

SURVIVAL OF MAMMALIAN STAGES OFMICROFILARIÆ IN VITRO

MARGARET TUMA HPAY.

Department of Bacteriology,Faculty of Medicine,

University of Rangoon,Burma.

SIR,-The letter by Colonel Bird and Mr. Menon 2

(who stated that they did not know of any similar reports)on the survival for 24 days of Microfilaria bancrofti instored blood at temperatures of 4-6°C suggests that thefollowing records may be of interest.

Takeshito and Okuda 3 kept Mf. bancrofti alive for 23 days incattle-heemoglobinised saline ". No further developmentwas observed. Coutelen kept Mf. bancrofti alive for 33 daysin vitro during which period the worms increased slightly insize and exsheathed. Taylor 5 suggests that exsheathment maybe influenced by the osmotic pressure of a culture medium.Fullebom maintained Mf. immitis in whole blood for 4-7

weeks at 0°C, but for only a week at " room " temperature.

In Taylor’s ° experiments Mf. loa and Mf. immitis remainedalive and morphologically normal for 10 days and 14 daysrespectively in horse-serum/dilute Tyrode containing erythro-cytes of the respective hosts. Mf. loa showed division of G cells1 and 2 after 10 days. Mf. bancrofti survived for 8 days in twomedia containing horse serum and Tyrode, and horse serum,glucose in Ringer, and Parker 199, respectively. The tempera-ture at which these loa, immitis, and bancrofti microfilariae werecultured was approximately 22°C. Mf. loa and Mf. immitis werealso stored by Taylor 7 at -79°C in glycerol/serum, and at" room " temperature in oxygenated blood, for 4-7 days.Micronlarise at -79°C showed vacuolation at the end of this

period. Those surviving at room temperature were normal inappearance and activity.Ghosh 8 kept Mf. bancrofti alive in:(a) Hydrocele fluid and hydrocele fluid mixed with human venous

blood up to 19 and 21 hours respectively at 37OC;(b) citrated venous blood up to 24 hours at 37°C;(c) hydrocele fluid and hydrocele fluid mixed with human venous

blood up to 26 hours at 16-27°C,(d) hydrocele fluid and hydrocele fluid mixed with human venous

blood up to 28-40 and 22 hours respectively at 4°C.We have been able to keep Mf. bancrofti alive in sealed cover-

glass preparations of oxalated venous blood for over 41 and 63hours respectively at 27-28°C in two cases.1. Mourant, A. E. The Distribution of the Human Blood Groups. Oxford,

1954.2. Lancet, 1961, ii, 721.3. Takeshito, S, Okuda, M. Igaku Chûô Zasshi. 1925, 23, 3. Cited by

Taylor (ref. 5).4. Coutelen, F. Ann. Parasit. hum. comp. 1929,7,399. Cited by Taylor (ref. 5).5. Taylor, A. E. R. Exp. Parasit. 1960, 9, 113.6. Fulleborn, F. Hanbd. Path. Mikroorg. 1929, 6, 1043. Cited by Taylor

(ref. 7).7. Taylor, A. E. R. J. Helm. 1960, 34, 13.8. Ghosh, H. K. J. trop. Med. Hyg. 1961, 64, 50.

O’Connor 9 attributed the longer survival of microfilarise atlower-than-room temperatures to the more rapid utilisation offood at higher temperatures. The period of survival wouldalso, presumably, depend on the individual ages of the worms.

VISCERAL PAIN

F. R. BROWN.

SIR,-May I comment on your Occasional Survey ofNov. 11 ? ?You referred to various theories which I thought had long

since been consigned to well-merited oblivion. Is the visceralperitoneum pain-sensitive ? Every house-surgeon knows thatthe pelvic colon can be opened with knife, cautery, or scissors,and a Paul’s tube tied in with a purse-string suture, with nopain to the colostomy patient. The stimulus is not adequatein either quality or quantity. We know that light, heat, andsound radiate, but does pain radiate any more than taste orsmell ? And by what mechanism does pain radiate from loin togroin-distally along afferent nerves ? Why are we unawareof our livers rubbing against the parietal peritoneum, which,like the cornea, articular cartilage, and synovial sheaths, has notactile sensation but, for our wellbeing and protection, anexquisite sense of pain ?

Aristotle asked " Why is it that an object held betweencrossed fingers appears to be two ?" In 1942 10 I answered thisand also the question: " Why is abdominal pain so oftenexperienced at a distance from the organ (or tissue) in which itis produced ?" I propounded the rule that pain produced in anorgan (or tissue) which migrated (by normal development) orwas artificially displaced (e.g., pedicle skin grafts) is invariablysituated in the primary relative position of the organ or tissue.There are many examples-appendicular colic, diaphragmaticpain, and testicular pain. All these organs or tissues got theirinnervation before they migrated or were displaced, and therelative reference map in the sensorium " believes " they stilloccupy their early embryonic position. In other words, therelative cerebral centres cannot be re-educated because wehave no awareness of the presence or position of the deeperstructures.

Dundee. F. R. BROWN.

DEMONSTRATION OF A HEPATIC UPTAKEDEFECT IN GILBERT’S DISEASE

SIR,-Intravenous 13’I-labelled iodipamide (’ Cholo-grafin’) is rapidly taken up by the normal liver." The

hepatic uptake can be monitored by two external scintil-lation detectors-one over the liver and one over the heart.The detectors are connected to count-rate meters and chartrecorders. A definite upward slope of the normal hepaticuptake tracing is readily distinguishable from the flat ordownward-sloping pattern in patients with various hepato-biliary diseases. The method is similar to the one usedwith 1311 rosebengal, but the results are much easier tointerpret.

Seven 131J-labelled iodipamide studies were performedon 4 patients with Gilbert’s disease (congenital non-haemolyticindirect hyperbilirubineeniia). The hepatic uptake was muchdepressed in all 4 patients every time they were examined,while their serum-bilirubin concentration ranged between0-4 and 3-0 mg. per 100 ml. When 131I rosebengal was givento each of these 4 patients upon the completion of the iodipa-mide test, the hepatic uptake of this substance was normal.The bromsulphalein retention at 45 minutes after a dose of5 mg. per kg. was repeatedly normal in 2 patients; in 1 it

9. O’Connor, F. W. Res. Mem. Lond. Sch. trop. Med. 1923, no. 4.10. Brit. med. J. 1942, i, 543.11. McLaren, J. R., Galambos, J. T., Weens, H. S. Amer. J. Roentgenol. 1961,

86, 768.