October 25, 1917] 



NATURE 



143 



THE ^TUDY OF LIFE. 

 The Study of Animal Life. By Prof. J. A. Thorn- 

 son. Revised edition. Pp. xvi + 477. (London: 

 John Murray, 1917.) Price 65. net. 

 117 OR about a quarter of a century this book 

 -*■ ... has had an apparently useful life as 

 an introduction to zoological science." With 

 these words Prof. J. Arthur Thomson begins his 

 short preface, and he is well and handsomely 

 ■entitled to them. The book is not a large one, but 

 it abounds in information, and the author sets it 

 all forth in an easy way, with the practised skill of 

 an old hand at teaching. The first part contains 

 a few eloquent chapters on such themes as the 

 "Wealth of Life," the "Web of Life," and the 

 ^'Social and Domestic Life of Animals," and 

 closes with a slighter sketch of the physiological 

 functions and activities of the body ; the second 

 part, which is copiously illustrated, deals with 

 structure and classification ; the third, in like 

 manner, with embryology; and the fourth and 

 last with the facts and theories of evolution. 



The array of facts is remarkable, and not less 

 so is the immense number of recent or current 

 theories which are dealt with or touched on in the 

 book. Lamarck and von Baer, Spencer and 

 Haeckel, Galton, Mendel and De Vries, and a 

 hundred more, all find their place in a brief historic 

 survey; they are all duly honoured, and occasion- 

 ally criticised — but the book is not written for 

 the sceptic. In writing a chapter on "Vitality " 

 I (as Prof. Thomson does not shrink from doing) 

 he calls in a little host of thinkers and philosophers 

 ito help him — Huxley and Haeckel, Clifford and 

 F Joly, Child and E. S. Russell and Driesch ; he 

 [leans in the end to views which he himself has 

 [done much to promulgate : " that we require 

 [ultra-material, notably historical, concepts for 

 [•describing organisms. For the organism is a 

 )sycho-physical individuality (a mind-body or 

 ly-mind) which has enregistered within itself 

 le gains of experience and experiment and has 

 sver its conative bow bent towards the future." 

 In all popular books, however good they be, 

 /en as this one is, there is an inevitable tendency 

 to make use, without more ado, of old familiar 

 lementary statements, which are by no means 

 Iways sound ; just as the classical scholar, for 

 instance, is (or used to be) too apt to take his 

 ;xts for gospel, and to shirk the weary work of 

 ;arching manuscripts. There is at least one 

 ich case, I think, where Prof. Thomson falls 

 Into error — in regard to the very common and 

 familiar subject of the retraction or "sheathing" 

 a cat's claws; at the same time, if he offends. 

 does so in good company. His drawing (on 

 35) is a familiar one, closelv resembling 

 Gvart's, but it is not accurate; the figure "III.," 

 )r the third phalanx, points to the head of the 

 :ond. But, and this is the important thing, 

 rof. Thomson explains the mechanism by saying 

 lat "the claw is retracted into its sheath — an 

 Idaptation for keeping it sharp when the animal 

 NO. 2504, VOL. 100] 



is at rest or is simply walking." In like manner, 

 Huxley talks of the claws being "completely re- 

 tracted within the sheaths of the integument, 

 when the animal does not desire to use them " ; 

 and Max Weber speaks of "die in der Haut 

 zuriickziehbaren Krallen, wodurch sie scharf 

 bleiben.'' But the fact is that the "sheath " is 7 

 very unimportant, if not wholly superfluous, part 

 of the mechanism. Owen and Mivart do not men- 

 tion it at all. It is a mere ruckle of skin, which 

 neither qovers nor protects the sharp point of the 

 claw. John Hunter describes it with perfect 

 accuracy: "The skin which covers the last 

 phalanx is very loose ; and when this phalanx is 

 drawn up or back, the skin covers a great deal 

 of the root of the claw." But the really important 

 fact is (as John Hunter was, I think, the first 

 to show) that the last phalanx, claw and all, is 

 crooked up or back, in a state of over-extension ; 

 so that the claw is raised off the ground — almost 

 precisely as the hammer in a pianoforte is raised 

 off the string. D. W. T. 



OUR BOOKSHELF. 



The Cancer Problem: A Statistical Study. New 

 edition. By C. E. Green. Pp. ix+140.' (Edin- 

 burgh and London: W. Green and Son, Ltd., 

 1917.) 



It is well known that the incidence of cancerous 

 diseases varies considerably in different districts 

 and in different occupations. In this book Mr. 

 Green has attempted to find some factor which 

 will explain this difference in incidence, and he 

 has critically examined the local distribution of 

 cancer in different districts, particularly in Scot- 

 land, and the conditions which obtain in those 

 districts. He finds that cancerous districts, as a 

 rule, are particularly associated with the burning 

 of coal as fuel, while in the non-cancerous ones 

 wood or peat is the staple fuel. Thus in Nairn- 

 shire, which has the highest mortality figure from 

 cancer in Scotland, the cancer deaths for the last 

 ten years are confined to a definite area, while the 

 rest of the county (100 square miles) is entirely, 

 free, and in the cancerous area coal is entirely or 

 partially used as fuel, while in the non-cancerous 

 area peat is universally used. The same holds 

 good for other parts of the country. Thus, in the 

 Orkneys, which, as a whole, have a cancer mor- 

 tality slightly above that for Scotland, Stenness 

 has a cancer death-rate of i out of 42 from all 

 causes and peat is the only fuel, while in Sanday, 

 where coal alone is burned, the cancer death-rate 

 is I out of 9 from all causes. A strange anomaly, 

 however, was met with. In Birsay and in St. 

 Andrews, in the Orkneys, the cancer mortality is 

 practically as great as in Sanday, yet peat only 

 is burned. Investigation showed that the peat 

 used in these two districts is peculiar, being hard 

 and stony and having a high content of sulphur like 

 coal. From these and other facts the author con- 

 cludes that a high sulphur content of the fuel is 



