March 2, 1922] 



NATURE 



267 



warfare (it is not too late, because it can still come under 

 Warfare) in which this important subject would receive 

 full treatment and in which the activities of British 

 chemists would obtain recognition. It is a curious 

 let that the need for such an article was emphasised 

 Sir Edward Thorpe himself in the review he wrote 

 on the book published recently by Prof. Moureu in 

 which this distinguished French chemist describes the 

 activities of his own countrymen. In the next edition 

 The article on chemical warfare might well follow that 

 in chemical affinity. 



One is glad to note that the old article on vegeto- 

 .ilkaloids is to be abandoned, and the different subjects 

 are to be treated ' under their own heads; thus there 

 is an excellent article on cinchona alkaloids by B. F. 

 TI. and 0. C, which gives a full account of these 

 important substances. The articles on the natural 

 . olouring matters and allied substances by A. G. P. 

 ire especially noteworthy, as are those on certain 

 Irugs, which fall within this section, by G. B. It 

 > articles such as these which render the dictionary 

 idispensable to the research worker, because they 

 Ive in a clear and concise manner all the essential 

 details of the chemistry of the substances dealt with 

 and do not confuse the issue by a mass of irrelevant 

 data. It is usually difficult to find information of this 

 kind elsewhere. 



Of the longer articles on subjects of general interest, 



those on carbon, coke manufacture, and recovery of 



hy-products by W. A. B. and E. R., copper cyanides 



by T. E., distillation by S. Y., and gaseous explosion 



by W. A. B. and R. V. W., have been brought up 



to date but otherwise retain the features which have 



rendered them so useful in previous editions. 



There are some completely new articles, and, of 



iiese, that on colour and chemical constitution by 



E. R. W. is particularly interesting. Most chemists 



will be familiar with the book on this subject which the 



-ame author contributed to the series of monographs 



n industrial chemistry edited by Sir Edward Thorpe, 



and although they may not all agree with many of the 



\iews expressed therein, they cannot but acknowledge 



' hat the account given is a fair and clear description of 



ur present position in regard to this very complex 



question. The present article may be described as a 



precis of the book, and is well worth perusal. Another 



new article is that by J. N. F. on the corrosion of 



metals. This is a subject which this chemist has made 



lis own, and there are few who can write on it with 



- reater authority. It is well written, and presents the 



abject from a point of view which cannot fail to be 



•iteresting. The article on dyeing remains much the 



sime as in former editions. One wonders if the tables 



lur detecting colours on the fibre, which occupy fifteen 



NO. 2731, VOL. 109] 



pages, are really worth the space. It may be noted in 

 passing that although the excellent article on cholesterol 

 is signed I. S. M., the name of this distinguished lady 

 does not appear among those of the eminent con- 

 tributors at the commencement of the volume. 



J. F. T. 



A New View of Fertility. 



The Law of Births and Deaths : Being a Study of the 

 Variation in the Degree of Animal Fertility under the 

 Influence of the Environment. By C. E. Pell. Pp. 

 192. (London: T. Fisher Unwin, Ltd., 1921.) 

 i2s. 6i. net. 



IN the issue of Nature for September 22, 192 1, 

 p. 105, appeared an article on " Causes of Fluctua- 

 tion of the Birth-rate," the statements and speculations 

 in which are usefully supplemented in the present 

 volume, which is a valuable contribution to the dis- 

 cussion of this important problem. The main thesis 

 of the book is that the decline of the birth-rate is not 

 explicable on the hypothesis that it is due to the 

 deliberate evasion of child-bearing, but that it can be 

 explained as the result of a natural law the function 

 of which is to adjust the degree of fertility to suit 

 approximately the needs of the race. Much ingenuity 

 is displayed in arriving at the conclusion that the 

 response to the action of the environment in the degree 

 of fertility bears an inverse proportion " to the intensity 

 of the nervous charge," and that the principle involved 

 is a law governing the union of sperm cell and ovum. 

 Unlike Doubleday, whose theory was that a plethoric 

 condition of the organism is unfavourable to fertility, 

 Mr. Pell regards food as only one factor and thinks 

 there is good reason for believing that cerebral develop- 

 ment and mental activity are far more important than 

 the supply of food. In this respect his theories approxi- 

 mate to the well-known views of Herbert Spencer as 

 to the inverse relationship between ability to maintain 

 individual life and the ability to multiply. 



The arguments by which the above propositions are 

 supported are ingenious and suggestive, although 

 occasionally weak and doubtful points are presented 

 with as great confidence as strong arguments. Thus 

 the author argues from very imperfect data that the 

 sale of contraceptive articles does not take place on a 

 scale large enough to account for the lowered birth- 

 rate, and he assumes the accuracy of the limited data 

 available as to sterility and small families in circles 

 where contraceptive methods are or are not practised. 

 Such data would need to be corrected for age distribu- 

 tion of the married couples under comparison and for 

 the duration of marriage before valid inferences could 

 be drawn. Even then it would scarcely be practicable 



