REVIEWS 181 



the complex appear simple with that of discriminating, with accuracy, between the 

 more and the less essential. 



The book is so well known as a full, clear, and reliable guide to elementary 

 work, that no detailed description of its contents is necessary. 



The present edition differs but little from its immediate predecessor. The 

 ninhydrin reaction has been introduced, but exercises on the analysis of simple gas 

 mixtures such as the atmosphere, expired air, and the blood gases are again omitted. 

 This omission is a little surprising. The apparatus required for simple gas analysis 

 is neither complicated nor costly, and affords valuable practice both in measurement 

 and in calculation. The physical aspect of Chemical Physiology, somewhat 

 scantily and disconnectedly presented, is still relegated to the Appendix. It may 

 be predicted that, in course of time, this section will be more fully treated and 

 transferred to its proper place in the body of the work. 



The book is admirably illustrated, with a coloured plate (osazone crystals), with 

 structural formulae, and with 71 clear diagrams showing (amongst other things) 

 chemical products and apparatus. Diagrams of the last type are particularly 

 helpful in elementary work and cannot be too numerous. One would welcome, 

 for example, the inclusion of apparatus for extraction and for filtration amongst 

 the excellent illustrations already provided. 



The text is well printed, unusually well spaced, and therefore exceptionally 

 easy to read. 



The work is, in short, as good as ever, and its continued success appears tc- 



be assured. 



W. L. Symes. 



The Biology of Tumours. By C. Mansell Moullin, M.D., F.R.C.S. [Pp. 55.JJ 

 (London : H. K. Lewis & Co., 191 6. Price 2s. 6d. net.) 



In this volume the author deals more thoroughly with the views which he had 

 already expressed on the biology of tumours in the Bradshaw Lecture for 1912. 

 A scheme of classification of tumours is advocated which is based on their mode 

 of origin, and from this point of view they are divided into two classes. Those in 

 the first class are due to the retention, within the organs or tissues, of cells whose 

 development has been arrested, and which are consequently able to manifest their 

 power of reproduction when a suitable stimulus, such as chronic irritation, is 

 provided. Those in the second class are due to defects in structural development. 

 With the exception of a few comparatively rare types all tumours belong to the 

 first class. 



No subject in the whole of pathology is so difficult as that of tumours, and in' 

 endeavouring to place their origin and classification upon a scientific basis the- 

 author has undertaken a task of the first magnitude. He has presented his- 

 theory, which in some respects is a combination of Cohnheim's theory of " cell- 

 rests" and Adami's theory of the "habit of growth," in a clear and masterly way,, 

 the attention of the reader is held throughout the book, and a powerful stimulus- 

 to thought on the vexed question of tumour formation is provided. 



The general adoption of the suggested scheme of classification would, however,, 

 virtually amount to an acceptance of the above theory of the origin of tumours, 

 and it is possibly better, for the present at any rate, to rely on the older methods ■ 

 of classification, which take into consideration the structure of the tumour, and. 

 which are for this reason of some practical value. 



J. W. Cropper. 



