278

lations may have originated in some such selectiveprocess ; and bacteriophage, instead of being regardedas a mere academic toy, must be suspected of possiblyvery sinister activities in epidemiology. Such specu-lation apart, Dr. HEwrrr’s evidence suggests that ithas had, and still has, an important r6le in bacterialevolution.

1. H.M. Stationery Office. 1952. Pp. 216, 9s.2. Ratcliffe, F. N., Myers, K., Fennessy, B. V., Calaby, J. H.

Nature. Lond. 1952. 170, 7.

Annotations

OVERCROWDING IN PRISONTHERE can be worse things in prison than iron bars,

and sleeping three to a cell is probably one of them.In its seventh report the Select Committee on Estimates 1

deplores that 4500 men in our prisons are sleeping in thisovercrowded way. The reason is not far to seek, for theprison population has now risen to over 25,000 men andwomen-twice as many as before the war. It is ironicalthat this increase is in part due to the Criminal JusticeAct of 1948, which, with the aim of reforming people andnot merely deterring them from crime, permits longersentences. The additional responsibilities which the Actimposes have unfortunately fallen on the prison organisa-tion at a time when it still has not made good war-timedeficiencies in accommodation and staff, and the problemsof overcrowding are aggravated by those of under-

staffing. Not only are there too many prisoners but thereare too few warders. As a result the prisoners spend longhours of boredom and near idleness in their cells whilethe warders habitually put in overtime. The committeedislikes both the short working week of the prisoners-sometimes as short as 22 hours-and the long workingweek of the warders ; it thinks that overtime in thelong run is neither economical nor efficient. Much of the

indiscipline, everyone agrees, is due to a comparativelysmall group of prisoners. The worst prisoners are notusually the worst criminals, and the committee urges thePrison Commissioners to give high priority to building aseparate prison or prisons where these psychopathictrouble-makers could be not only segregated but alsostudied and treated.

Overcrowding brings problems of health as well as

discipline, and the committee is especially concerned atthe increased risk of infection, particularly of tuberculosis.Some arrangements have been made to examine prisonersby mass-radiography units ; but the initiative is left tothe senior medical officer in each prison, and the com-mittee recommends that the Director of Prison MedicalServices should approach the Ministry of Health to ensurethat prisoners get their fair share of the services of theseunits. The prison medical service, like the other branches,is understaffed. Instead of 52 full-time doctors, it has

only 42 : and few recruits come forward, for the salariesare unattractive. The committee particularly regretsthat it is no longer possible to produce a medical andpsychiatric report of each boy and girl who passes throughthe borstal allocation centre, and urges an early returnto this pre-war custom.

MYXOMATOSIS AND RABBITS

IN the past fifteen months an artificially induced

epizoötic has killed many millions of rabbits in Australia,thus demonstrating for the first time that a pathogenicagent can he successfully put to work against a mam-malian pe",t.2 Myxoma virus, which may be related tothe pox group of viruses, has a species of Brazilian.. rabbit

"

as its natural host. and it was first recognisedin laboratory animals by Dr. H. B. Aragão, who alsosuggested its u-e in biological control. The work started

by Sir Charles Martin in 1933 at Cambridge showed that

the disease was highly pathogenic for wild and domesticrabbits, but was harmless for all domestic animals andfor most of the native fauna of Australia, as well asfor the imported European hare. Fears that the virus

might be the cause of serious infections in man havealso proved unfounded. Myxoma virus thus combinesextreme virulence for one animal pest with almost

complete avirulence for most other creatures, and itwas therefore an ideal pathogen to use in attempts atbiological control.

Field trials carried out before the late war in semi-arid

pastoral areas were inconclusive, but they did showthat the virus was transmitted among rabbits by thestickfast flea, whose limited mobility made it a poorvector. Some of the many ecological difficulties weresoon encountered ; for example, it was impossible toestablish and spread the disease where foxes were

lying in wait to pick off the first generations of lazyinfected rabbits. After the war the CommonwealthScientific and Industrial Research Organisation decidedto re-examine the possibilities of controlling the increas-ingly serious rabbit menace with myxoma virus, andbetween May and November, 1950, the virus was releasedseven times in the Murray valley. The immediateresults were disappointing, for the disease had no

appreciable effect on the numbers of rabbits. In Decem-ber, however, the disease suddenly flared up at one ofthe infected places, and soon reports came from manyother areas, including a place on the Darling river nearly400 miles from the nearest known point of infection.The wide dispersal of the virus and the intense localspread produced a remarkable epizootic within the nexttwo or three months, and it was thought that mosquitoes,moving under their own power or carried by high-levelwinds, were responsible. Nothing else could explainthe isolated outbreaks along the southern margins ofthe epidemic area in Victoria and in South Australia,nor an isolated outbreak almost in the centre of thecontinent. In the new year the epizootic gained moinen-tum, and by February, 1951, an area of 1000 square mileswas involved. The disease spread at remarkable speedthrough the rabbit population and killed 90% of them.River courses, creeks, and swamps were most heavilyinvolved, suggesting once again that water-breedingvectors were essential to spread. In such a large area,however, geographical conditions varied enormously;in the Murray valley, for example, only those rabbitswithin a few hundred yards of the water’s edge werekilled, whereas in south-east Queensland the diseasewas unbounded, and it was possible to drive for a dayor more through country that had previously been

swarming with rabbits and see only a few isolatedsurvivors.When the trials began it was known that myxoma

virus could be transmitted by two species of fiea andby several species of mosquito, but little was knownabout their performance in the field. It was found thattransmission was almost certainly mechanical and thatany blood-sucking arthropod was a potential vector.The epidemiology of the disease, and hence its practicalvalue in biological control, is largely influenced by theecology and habits of vectors, the strength of theirpreference for rabbit blood, and the length of time forwhich they are about in great numbers. In such a vastand varied area it was likely that different vectorswould have local predominance ; in the Murray valley.for example, Culex amrulzrostris was a principal vector.whereas on the Victorian coast and the off-shore island--4e(le.q catiiptorhytichus was the most important. Duringthe winter months of 1951 the disease continued to

smoulder, and ectoparasites may have ensured the

persistence which was necessary to the success of thescheme. In the summer of 1951-52 a closer study wasmade of the various vectors, and Anopheles annulipes,

279

which spends the day in the rabbit warrens, was foundto have played a predominant part. This third phaseof the epizootic has developed mainly in areas not

involved before, and attacks were most intense wheresuitable anopheles breeding-grounds were plentiful. Inthe Murray valley during 1951-52 this mosquito fore-stalled in time and outstripped in range the culicinevector of 1950, so that, instead of the disease -beingconfined to a narrow strip along the breeding-waters, itnow spread for as many miles as it had hundreds of yardsduring the previous summer. These entomologicalstudies have now covered a full cycle of the seasons,and the broad pattern of the ecology of the mosquitofauna shows a fairly clear succession of species, eachbecoming dominant as larval and adult habitats changein nature and extent.What of the practical results so far achieved in the

control of the rabbit pest in Australia ? What is likelyto be the ultimate effect of introducing myxomatosisinto the country ? Ratcliffe and his colleagues 2 approachthese questions cautiously, but in one sample area of100 square miles, where 64,000 acres were classed as

heavily infected before the epizootic, only 640 acres

remained so after it. In large parts of South Australia,Victoria, and New South Wales the number of rabbits isnow one tenth or less of the 1950 figure. Thousandsof farms have had their land cleared of rabbits, withan obvious and immediate increase in pasture growthand stock-carrying capacity. When the epizootic tookplace, rabbits were very numerous, even for Australia,and the seasons were favourable for the virus vectors ;in these circumstances the mortality was high and it isprobable that tens of millions of rabbits died. It is

reasonably certain that myxomatosis is now permanentlyestablished in Australia and it may soon becomemore uniformly distributed throughout the rabbit popu-lation, and thus be able to spread more rapidly underfavourable local conditions. But a final judgment isnot yet possible. A natural process of adjustmentbetween parasite and host may take place either by theemergence of virus strains of altered virulence or by thedevelopment of resistant generations of -rabbits, or byboth. These possibilities are being examined experi-mentally and there is already evidence that recoveryis commoner in the field than in the laboratory, where a100% mortality has been the rule.This interesting experiment is of immense practical

importance, and its Australian designers are alive to themany ecological and epidemiological opportunities thatit affords.

?-,

LARYNGEAL SPASM

THE larynx has been called the watchdog of the

respiratory tract. Perhaps it might be better named thewatchdog of the patient, because laryngeal closure--probably as a protective response-may follow harmfulstimulation of almost any part of the body. The risk ofsuch spasm has always haunted the anaesthetist. Whileon the one hand it protects patients from inhalation ofvomit, on the other it interferes with anaesthesia bymaking it difficult to introduce irritant vapours such as4ether into the lungs, and by rendering many operationsmore or less impossible under light anaesthesia. Whetherthe spasm by itself can cause the death of a patient is aquestion which anaesthetists have long discussed amongthemselves. It is doubtful whether death from this causealone ever takes place in ordinary clinical practice ;for when the anoxia and carbon dioxide accumulationreaches a certain point the patient gasps once or twiceand takes in enough air to get a grip on life again.The treatment of laryngeal spasm consists primarily

ill removing the causal stimulus. One of the first lessonsIf:’arnt by the young anæsthetist is that spasm of this sortduring induction of anesthesia with ether is best treated

by weakening the ether vapour inhaled and startingagain, rather than by pouring more ether on the mask.Similarly laryngeal spasm in the middle of an abdominaloperation is an indication for a pause in the surgicalwork before, and not after, an attempt to deepen theanæsthesia. The use of muscle relaxants to treat laryn-geal spasm in the presence of its causal stimuli can bevery dangerous, because the respiratory muscles are

paralysed at the same time as the laryngeal spasmrelaxes. This method should be adopted only by themost experienced anaesthetists. Artificial respiration bycompression of the chest is ineffective against severe

laryngeal spasm ; for the expiratory muscles are usuallyin spasm too. Even the worst spasm, however, quicklyresponds to removal of the ether mask. Then the lungscan be inflated with oxygen from an oxygen-filled bag,which is gently squeezed ; or, failing oxygen, air can beused. Very occasionally the larynx may have to be

exposed and a small-bore, smooth-tipped, firm cathetergently inserted between the cords-great care beingtaken to avoid damage to the larynx. Drugs have little,if any, place in the treatment of this condition, which isprimarily one of motor reflex activity.

1. Mills, C. A. J. Amer. med. Ass. 1941, 117, 1500.2. Reingold, I. M., Webb, F. R. Ibid, 1946, 130, 491.3. Leitner, Z. A. Lancet, 1943, ii, 474.4. Laws, C. L. J. Amer. med. Ass. 1941, 117, 176.5. Schiff, L. Ibid, p. 609.6. Eisenstadt, W. S. Minn. Med. 1942, 25, 861.7. Chitwood, W. R., Moore, C. D. J. Amer. med. Ass. 1952, 148,

461.8. Pelner, L. Ann. intern. Med. 1947, 26, 290.9. Powers, B. R. Ibid, 1948, 29, 558.

10. Mitchell, D. C., Vilter, R. W., Vilter, C. F. Ibid, 1949, 31, 1102.11. Armanino, L. P., Scott, W. S. Calif. Med. 1950, 72, 178.12. Weigand, C. G. Geriatrics, 1950, 5, 274.13. Kalz, F. J. invest. Derm. 1942, 5, 135.

REACTIONS AFTER VITAMIN-B INJECTION

THE vitamins of the B group are the ones most fre-quently given by injection. Untoward effects after suchinjections are uncommon, but two fatal reactions havebeen recorded ; in one case thiamine had been givenintramuscularly, and in the other 2 intravenously.Other less severe reactions, including circulatory collapse,have occurred not only with thiamine but with othermembers of.the group. Two types of major reactionfollowing the injection of thiamine have been described.3In one a condition resembling anaphyJactic shock mayoccur in sensitised persons, usually after a long course ofsymptomless injections. The other less dramatic typeproduces symptoms like those of thyroid overdosage-excitement, tremor, palpitation, giddiness, and insomnia.Intradermal tests have shown sensitivity to the vitaminin both types of reaction.4-6

Chitwood and Moore have lately reported what theyregard as the first case of severe anaphylactic shock afteran intravenous injection of vitamin-B complex. Circu-

latory collapse has also been reported after intravenousnicotinic acid 89 and folic acid.’ But most of the reactionsseem to have followed the use of thiamine.l1 Weigand 12analysed the reports of 143 physicians who gave thiamineby injection and found 179 cases in which there was areaction, but only 17 were described as serious. The lesspronounced reactions might, of course, be easily over-looked. Sensitivity to thiamine and other members ofthe group can be acquired ; in all the reported caseshypersensitivity developed only after repeated symptom-less injections, with the notable exception of nicotinicacid which caused circulatory collapse in 2 patientsimmediately after the first injection.9 10Acute vitamin-B deficiencies are rare in this country,

and the risks arising from injection of vitamin B must betaken into account when considering its advantages.Obviously there will be a stronger case in its favour whenabsorption by mouth is deficient. As a precautionarymeasure skin tests may be carried out, but it has beensaid that thiamine is an obligate weal-producing agent 13