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decline in the rate of growth. It is the function of life,as Hopkins shrewdly pointed out, to hold up that

dissipating energy at a useful level. For the last twentyyears: or more, interest has concentrated on the qualityrather than on the quantity of growth. At an earlystage the graft of embryonic tissue from the dorsal lipof the blastopore is capable of imposing its inherentpotentialities on, its new environment; in this way aneural canal is formed on any part of the embryo receivingthe implant. Yet at a slightly later stage the implant hasto accept the structural development of its host. Clearlyspecialisation of organising material has already begun.Joseph Needham found that the organiser.was a sterol, re-minding us of the chemical structure of certain hormones.

Hormones- appeared before the glands that were tohouse them .; and comparative morphology suggeststhat many of the glands had a more primitive functionthan that which they now possess. J. F. Gaskell showedthat in the lamprey there was a wide distributionof adrenaline-secreting cells, though as developmentincreased these became almost entirely confined to themedulla of the adrenal.The close association of nervous and endocrine systems,

once achieved, has never been dropped, showing that itmust be of great advantage to the organism. Pathologyillustrates this by the observation that in anencephalicmonsters the fusion between cortical and medullaryportions of the adrenal does not occur. Loewi and Dalehave proved by the recognition of cholinergic and

adrenergic nerve-endings that every nervous stimulusis mediated through a chemical mechanism beforeaffecting the tissue cell.The chemical similarity between hormones as

regulators of normal metabolism and carcinogens asstimulators of abnormal growth has excited some

apprehension. Amphibian eggs subjected to " delayedfertilisation" illustrate this relationship. If the delayis short, serious imbalance of the sex-ratio ensues if the delay is longer, multiple liberation or formationof the organiser takes place, and multiple monstersresult; if the delay is very long, shapeless teratomatadevelop, which, if implanted into an adult frog, willgive rise to malignant growth, including even metastase,.This gradual transition from the normal to the franklymalignant must surely depend on environmental factors.It is, indeed, in connexion with the sex hormones thatthe overlap between the stimulus for cancer productionand the stimuli for the sexual cycle is the most obvious.But this overlap is also seen between the oestrogensand the primary organiser. There is strong support forthe opinion that the primary organiser is a sterol-likesubstance. In view of the exceedingly wide distributionof the primary organiser and the presence of oestrogensin coal-tar, it is significant that oestrogens have beenfound in some plant tissues. This reminds us of thoseother exogenous hormones, the vitamins ; and the sterol-like character of vitamin D provides another exampleof overlap between the various growth factors.

Reviews of Books

Leprosy- . (3rd ed.) Sir LEONARD ROGERS, K.C.S.I., M.D., F.R.C.P. ;

ERNEST MUIR, c.I.E., M.D. Bristol: John Wright. Pp. 280.25s .

THE third edition of this useful work records theprogress made in spite of the hindrances of war. Thesection on the distribution of leprosy has been broughtup to date, figures up to 1943 being included. Transmis-sion and causation are discussed in the light of recent’knowledge. Vaccination against smallpox may causelepra reactions, and in people previously unsuspected ofleprosy these have given rise to the mistaken idea thatthe disease may be spread by vaccination. Authenticatedinstances of infection have been reported, however,following arm-to-arm vaccination from a leper.Work on the lepromin test shows it to be of a different

nature to the tuberculin test, and of little value in thediagnosis of leprosy, but it serves to distinguish thelepromatous from the neural cases, the former givingnegative and the latter positive results. The relationshipof the two main types of the disease is reviewed in thelight of increased knowledge. The newer drugs nowbeing used are mentioned, including’ Diasone,’ , Promin,’penicillin, and Asiaticoside.’ ’

Thinner paper is used than in the former edition, andthough a bibliography has been added and the numberof pages increased by 20 the volume is smaller. Thegood plates and diagrams have been supplemented by8 new illustrations. I

Clinical NeurologyBERNARD J. ALPERS, M.D., SC.D., professor of neurology,Jefferson Medical College, Philadelphia. Philadelphia :F. A. Davis. Pp. 797.$8.

Professor Alpers states his intention of presentingneurology in such a manner as to make it intelligibleto medical students and general practitioners, and hehas chosen to do so by giving " a. concise or detailedaccount of all the neurological conditions to be encoun-tered in practice." Neurology above all other subjectsmust be based upon a sound knowledge of anatomy andstill more of physiology, for without a thorough acquain-tance with general principles the student or generalpractitioner cannot begin to recognise the disorders heencounters. Dr. Alpers fails to lay this necessary founda-tion. Nor can he be said to show due proportion inallotting space to different topics. For example, hedevotes two pages to fractures and dislocations of theatlas and only four to migraine ; psittacosis and goutare listed as " some of the more common conditions "causing headache ; and space is found for aspergillus

infection of the meninges, which is said to be a " notuncommon " infection of the orbit. Some statements,moreover, are misleading: the pupil described byArgyll Robertson is small and reacts to accommodationbut not to light, but Dr. Alpers describes the ArgyllRobertson pupil as one which is typically small, butmay be dilated, and responds to accommodation butthe response may be so slight that it is difficult to see,or even absent. The illustrations and format are worthyof a better book. *

Year Book of General Surgery 1945Editor : EVARTS A. GRAHAM, M.D., professor of surgery,Washington University. Chicago : Year Book Pub-lishers. London : H. K. Lewis. Pp. 736. 188.

THIS yearbook is well known in this country and the1945 edition is as usual a mine of information. Itsummarises recent surgical papers of importance, withall too few comments by the editor. The Britishliterature receives a fair share of attention, thoughthe book is mainly based on American experience.From the standpoint of British readers it is a pity thatorthopaedics and urology should be treated in separatevolumes, for specialisation has not’ reached such a

degree here as in America and the-general surgeon oftenfaces problems in both these’ specialties. Since theinformation in this book is new much of it is necessarilyunproven or controversial; but from such a wealth ofstimulating matter any surgeon will find something tolearn and plenty to think about.

An Introduction to Medical Science

(3rd ed.) WILLIAM BOYD, M.D., F.n.c.p., professor ofpathology and bacteriology in the University of Toronto.London : Henry Kimpton. Pp. 366. 18s.

AN introduction should enable the novice to see what’swhat. Professor Boyd keeps this in mind together withthe special needs of the nursing profession, for whomhis book is intended. In his friendly style, and by theuse of simile and allusion, he explains the prime factsof medical science, and except when he discusses thetreatment of pneumonia does it without using jargon.After setting out general principles in disease processes,he describes the chief diseases of the various organs,and finally the principles of prevention, treatment, andlaboratory investigation. The vast subject has beencondensed with judgment, though there is occasionalrepetition and British readers may wonder why tular-aemia has a paragraph to itself. The chapter on theprinciples of treatment is new to this edition. It isa pity that the quality of the text is not maintained inthe illustrations, for though many are good, fully a fifthare in some way unsatisfactory.