572 SCIENCE PROGRESS 



subject is hardly susceptible to arrangement according to broad results and 

 general conclusions, and the chapter hence takes the form of a clearly written 

 summary of the various types of reactions — unimolecular, bimolecular, and so 

 on — with well-chosen illustrations from organic chemistry. 



In the chapter dealing with the relationships between physical properties and 

 structure, Prof. Cohen has given a particularly lucid account of the development 

 and present state of most of the subject. If any criticism must be made, it is that 

 photographs and descriptions of apparatus seem to be superfluous in a work of 

 this kind, which is already sufficiently bulky. 



One cannot help thinking that the author has been less happy in discussing 

 colour and the absorption of light. The section on absorption-spectra is relegated 

 to the chapter on physical properties, which is inconsistent with the identity of 

 visible and of invisible colour to which the author himself calls attention. The 

 present stage of our knowledge of the influences of structure on light-absorption 

 is one of classification chiefly; and many of the so-called "theories" of colour 

 are hardly more than summaries of the compounds which possess the faculty of 

 absorbing light rays. Greater discrimination in this direction would have been 

 acceptable, and the sifting and blending processes before referred to could have 

 been utilised in this chapter to great advantage. 



The volume contains few noteworthy misprints ; the reproduction of the 

 photographs of absorption-spectra, however, might well be improved. There 

 are full indexes, and references are given throughout both to original papers 

 and to larger monographs. 



On the whole, then, the virtues of the book, which are many, are to be found 

 in the clear presentment of facts and of separate theories ; and its chief fault is 

 one of omission, consisting of insufficient correlation of these theories. Never- 

 theless, the two volumes together form a valuable acquisition, and will earn a wide 

 circulation. Irvine Masson. 



Organisclie Arsenverbindungen und ihre chemotherapeutische Bedeutung. 

 By Dr. M. Nierenstein. (Stuttgart : Sammlung Chemischer und 

 Chemisch-technischer Vortrage, vol. ix, 1912.) 



After a short historical sketch of the employment of arsenic and its compounds 

 in medicine from the earliest times, the author gives a complete list of the arsenical 

 compounds prepared by Bunsen in his investigation of the Kakodyl series, and 

 also a selection of the more important substances synthesised by Michaelis ; then 

 follows an account of Ehrlich's so-called Reduction Theory of the mechanism of 

 the action of the azo-dyes Trypan Red and Trypan Blue and of Atoxyl on 

 trypanosomes, a theory which led ultimately to the discovery of Salvarsan. Some 

 space is next devoted to the discussion of two alternative theories described as 

 the Oxidation Theory of Breinl and Nierenstein and the Partial Cell-function 

 Theory of Uhlenhuth, in connection with which the pharmacological action of 

 a number of synthetic arsenic compounds is described. The monograph may 

 be welcomed as a useful summary of a somewhat extensive subject. 



The Continent of Europe. By Lionel W. Lyde, M.A., F.R.G.S. [Pp. xvi + 

 446. With 12 coloured maps, and numerous smaller maps in the text.] 

 (London : Macmillan & Co., 1913. Price ys. 6d.) 



It is to be hoped that the users of books read the prefaces that are prefixed by 

 conscientious authors. Mr. Lyde's preface is unusually helpful, and is an intro- 



