i8 9 6. VERWORN'S GENERAL PHYSIOLOGY. 407 



life is an ordinary and not a supernatural result of the development of 

 our planet. We know life only by its qualities, and these qualities, 

 one and all of them, are necessary results of the interaction between 

 the chemical, physical, and morphological properties of the mixture 

 we call protoplasm and the surrounding forces. Similarly his discus- 

 sion of death leads to a plain conclusion: no definite material system, 

 like a piece of protoplasm, no definite complex of activities like life, is 

 immortal ; in the whole world all that is immortal and eternal is 

 elementary matter with its forces. 



The fifth chapter, of 120 pages, is upon stimuli and stimulation, 

 and perhaps is the most directly interesting to physiologists. After 

 treating of the nature of stimulation, the author deals with the 

 mechanism of the different kinds of stimulation, in this following 

 rather more closely than is his wont the familiar course of a physio- 

 logical treatise. Thereafter he describes the less famiiiar phenomena 

 known as tropism, and includes figures and descriptions of chemo- 

 tropism and galvanotropism, which will be new to most readers. 



The last chapter, entitled the mechanism of life, contains a large 

 amount of material that, so far as we know, has not yet found its way 

 into text-books. It is inspired more definitely than the other sections 

 of the book by the individual conceptions of the author. He discusses 

 Roux's view of the mosaic nature of living bodies, and details his con- 

 ception of biogenes, the ultimate vital particles or units which, to a 

 certain extent, correspond to the biophores of Weismann, the physio- 

 logical units of Herbert Spencer, the gemmules of Darwin, the 

 pangenes of De Vries, and the idioblasts of Hertwig. The corre- 

 spondence, of course, is of the vaguest kind, as these theoretical units 

 are in every case merely a concrete expression of their authors' con- 

 ception of the nature of vital activities. In this chapter, too, occur 

 Verworn's special views as to the function of the nucleus, views which, 

 as is well-known, differ from those held by most biologists. We have 

 no desire to object to the inclusion of individual views ; indeed, after 

 so careful and impersonal a discussion of the main parts of his subject, 

 as is to be found in five-sixths of the volume, the reader is glad 

 to become on more intimate terms with the author. 



In so vast an array of subjects, it must necessarily happen that 

 any biologist reviewing the volume should come upon statements he 

 would prefer to modify, conclusions he would wish to combat. But 

 the conception of physiology taken by the author, and the all- 

 embracing treatment he has adopted seem to us so admirable from 

 the point of view of stimulating thought, and so beyond praise in these 

 evil days of narrow specialism, that we have thought it a duty, as we 

 found it a pleasure, to describe rather than to discuss the volume. 

 We believe that Verworn's "General Physiology" is the most notable 

 book we have read for many years, and that it, and the successors it 

 will call into existence, will have a permanent influence on biological 

 teaching. P. C. M. 



