i66 



NATURE 



[February 9, 1922 



capable of surviving in high concentration of this 

 acid. To this end he recommended, and himself 

 practised, the imbibition of large quantities of 

 soured milk. 



Metchnikoff's preoccupation with the disadvan- 

 tages of senility have been misunderstood and mis- 

 interpreted. Although his attention was becoming 

 unpleasantly directed in his own person to the effects 

 of a life of intense activity and mental excitement, 

 coupled with serious cardiac mischief, it is not to 

 be ascribed to the morbid introspection of an in- 

 valid. Old age is a legitimate subject for scientific 

 inquiry. It is not unnatural, but unfortunate, that 

 nobody becomes sufficiently interested in the prob- 

 lems of senility until their own age well-nigh pre- 

 cludes the possibility of a successful enterprise. 

 It was approached by Metchnikoff with ideas based 

 on broad biological principles, and most of his late 

 work was really concerned to find' justification for 

 them. 



Elie Metchnikoff's enthusiasm for his theory of 

 orthobiosis was maintained actually until the end 

 of his life, and the last chapter of the biography 

 contains many records of his mental attitude on 

 contemplating death at short range. He was anxious 

 that these should be recorded as so few with the 

 capacity to analyse their mental processes retain 

 their intellectual powers until the end of life. 



His wishes have been piously complied with, and 

 his observations, when confronted with impending 

 dissolution, are faithfully recorded as his final con- 

 tribution to his theory of the development of the 

 death instinct. 



The book is more than an account of the interest- 

 ing discoveries of Elie Metchnikoff and their far- 

 reaching importance in natural history; it is a 

 human document, an account of the mental adven- 

 ture of a striking personality, with contemporary 

 science as a setting, told with a naivete reminiscent 

 of Marie Bashkirtseff. 



The translation is excellent, and little if any of 

 the charm of the original French is lost. The bio- 

 graphy contains as frontispiece a characteristic pic- 

 ture of Metchnikoff in his laboratory, and concludes 

 with a useful bibliography of all his published 

 writings. 



Electrical Measurements. 



Absolute Measurements in Electricity and Mag- 

 netism. By Prof. A. Gray. Second edition, re- 

 written and enlarged. Pp. xix-f837.^ (London: 

 Macmillan and Co., Ltd., 1921.) 42^. net. 



ALL physicists are familiar with the first edition 

 of this important work, which, completed in 

 1893, has long been regarded and used as a standard 

 NO. 2728, VOL, 109] 



treatise on electrical measurements. In introducing 

 the second edition Prof. Gray refers at the outset to 

 a certain lack of interest shown by physicists at the 

 present time in the theory and practice of absolute 

 measurements, and it is undoubtedly the case that, 

 in our universities at any rate, the subject receives 

 less attention than was formerly devoted to it. The 

 principal reason for this change may be traced to 

 the nature of such work as the experimental deter- 

 mination of absolute electrical units, and the accu- 

 rate comparison of secondary standards with them, 

 and also to the great importance which work of this 

 kind possesses. Few, if any, of our university 

 laboratories are sufficiently well equipped for the 

 prosecution of researches in which the construction 

 of apparatus and the carrying out of measurements 

 of the highest precision are involved ; and so neces- 

 sary is this work recognised to be that special labora- 

 tories, such as the National Physical Laboratory in 

 this country, and the Bureau of Standards at Wash- 

 ington, have been established, at which it can be 

 more effectively organised and carried out, and at 

 which the research worker in any of the universities 

 may have his measuring instruments accurately stan- 

 dardised. Thus the apparent decline of general in- 

 terest among physicists in methods of absolute 

 measurement is not due to any diminution in the im- 

 portance of the subject, but to the fact that the 

 practice of these methods is now more concentrated 

 in institutions specially equipped for the purpose. 



A second reason for the change may be found, as 

 suggested by Prof. Gray, in the fact that new and 

 fascinating subjects of study, mainly consequent 

 upon the discovery of the X-rays and radio-activity, 

 have arisen which have been taken up with enthusi- 

 asm in our universities, and have to some extent 

 diverted attention from absolute measurements of the 

 classical kind. While it is of the greatest import- 

 ance that research into the problems of modern 

 physics should be pursued as vigorously as possible, 

 it is no less important to the future of the science 

 that the endeavour to attain greater accuracy in our 

 standards and methods of measurement should not 

 be relaxed. It may well be that the future trend of 

 physical theories will be largely influenced by the 

 degree of accuracy with which some of the important 

 constants can be determined. 



The new edition of Prof. Gray's book will be 

 welcomed as a full and clear statement of the 

 present position regarding accurate electrical 

 measurements. There is probably no other book 

 which contains so full an account of the classical 

 experiments for the determination of electrical units 

 and constants, and the many detailed abstracts of 

 original memoirs give the book a special value as a 

 work of reference. 



The principal changes found in the new edition 



