676 



NATURE 



[July 28, 192 1 



portant paper on the distribution of temperature 

 in an explosion cylinder was communicated to the 

 Royal Society, and the discussion aroused on 

 these matters led to the formation of the Gaseous 

 Explosions Committee of the British Association, 

 of which Sir Dugald Clerk was chairman, and 

 Hopkinson secretary. Much, probably most, of 

 our recent knowledge of the theory of the internal- 

 combustion engine has sprung from the labours 

 of that committee, and to the advance made Hop- 

 kinson was a most important contributor. It is 

 sufficient, perhaps, to mention his last paper on 

 the subject, "On Radiation in a Gaseous Ex- 

 plosion," communicated to the Royal Society in 

 igio; the work thus begun has recently been 

 brought to a most satisfactory conclusion by his 

 pupil and assistant, Mr. W. T. David. In con- 

 clusion, reference should be made to a lecture 

 at the Royal Institution, 191 2, on "The Pressure 

 of a Blow," and to the Royal Society paper on "A 

 Method of Measuring the Pressure due to the 

 Detonation of High Explosives," which led in a 

 simple way to results of marked interest. 



Enough has probably been written to show the 

 high value of the work Hopkinson did, and the 

 magnitude of the loss to engineering science 

 caused by his early death. To quote the words 

 of Sir J. J. Thomson, speaking as Master of 

 Trinity in a commemorative address, "our roll 

 of honour contains the name of no one who has 

 rendered greater services to his country." 



The New Medicine. 



The Principles of Preventive Medicine. By Prof. 

 R. T. Hewlett and Dr. A. T. Nankivell. 

 Pp. viii + 536. (London: J. and A. Churchill, 

 1921.) 215. net. 



THE object of Prof. Hewlett and Dr. 

 Nankivell in writing this book was to give 

 an outline of the principles and practice of pre- 

 ventive medicine "so far as it seems to concern 

 the medical student and the general practitioner 

 of medicine." That there was need for such a 

 book there is no doubt. All who are concerned 

 in any way with the teaching or practice of public 

 health and preventive medicine certainly must 

 agree that such a book was required, just as they 

 must agree that this volume by Prof. Hewlett 

 and Dr. Nankivell goes some distance towards 

 supplying the need. The preparation of the book, 

 the authors admit, gave considerable trouble, the 

 extent of the field to be covered rendering it 

 difficult to decide what to include and what to 

 omit. In all book-making this is always a difficult 

 thing, but in this case the authors have chosen 

 wisely, and in the twenty-one chapters and three 

 NO. 2700, VOL. IO7J 



appendices they appear to have made reference 

 to all the more important matters in respect of 

 which the medical student and the practitioner — 

 who, after all, are expected to play a great part 

 in the preventive medicine of the future — need in- 

 formation. 



As might be expected in a book prepared by 

 two practical men like Prof. Hewlett and Dr. 

 Na:iikivell, one a distinguished bacteriologist, and 

 the other a Medical Officer of Health of some years'" 

 standing, the information given is trustworthy. 

 Here and there in the writing, however, there is- 

 shown a tendency to leave the lines followed in 

 the ordinary medical books, and to indulge ia 

 what may almost be called "flights of fancy." 

 In a number of places the authors appear unable 

 to avoid the temptation to drop into poetry, and 

 to provide word-pictures in which they use much 

 more colour than appears to be essential in a book 

 intended for such dispassionate readers as medical 

 students and practitioners are, or should be. The 

 chapters in which the fancifulness and the over- 

 drawing are most frequently to be met are, curi- 

 ously enough, those in which serious writing and 

 strict accuracy of expression are most called for 

 — viz. those dealing with housing, infancy^ 

 motherhood, and school children— and though 

 there may be some who will appreciate the pic- 

 turesque and exaggerated phrasing at its true 

 value and find it helpful, it seems not unlikely 

 that more will regard it as objectionable and out 

 of place. In any case, it seems unfortunate that 

 in one of the first books on preventive medicine 

 the line here chosen should have been taken, and 

 the impression given that the subject is one which 

 is most suitably dealt with in a style more popular 

 than scientific. 



In the chapters dealing with infectious diseases 

 the authors have exercised greater restraint and 

 provided an amount of interesting, useful, and 

 sound information. These chapters are amongst 

 the most valuable in the book, and are particularly 

 noteworthy for a declaration against the ten- 

 dency to search out and find specific germs of 

 disease, and more or less in favour of the 

 view that, since they can be shown to change 

 their shape and even their virulence on occasion, 

 there is no such thing as constancy among micro- 

 organisms. It is not, therefore, too much to sup- 

 pose them capable of undergoing such transforma- 

 tions as will allow them to produce one type of 

 disease at one time and another of an associated 

 type at some other time. Another excellent chapter 

 — although by the medical student and practitioner 



1 it may be regarded as rather more full of arith- 

 metic and mathematics than is absolutely essential 



' — is that on vital statistics. Amongst readers 



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