AUTHOR'S PREFACE 



" Each living being must be considered a microcosm, a small universe, which 

 is formed from a collection of organisms, which reproduce themselves, which 

 are extremely small, and which are as numerous as the stars in heaven." 



Darwin. 



A glance at the numerous text-books on histology shows us that 

 many questions of great interest in scientific investigation are 

 scarcely mentioned in them, whilst many branches of knowledge 

 which are closely connected with histology are more or less 

 excluded. The student is taught the microscopic appearances 

 which are presented by the cell and the tissues, after these have 

 been prepared according to the different methods which are most 

 suitable to each, but he is taught very little of the vital properties 

 of the cell, or of the marvellous forces which may be said to 

 slumber in the small cell-organism, and which are revealed to us 

 by the phenomena of protoplasmic movements, of irritability, of 

 metabolism, and of reproduction. With regard to the different 

 subjects which he studies, if he wish to be in touch with the 

 progress of science, and to understand the nature and attributes 

 of the cell-organism, he must read the works of specialists. 



It is not difficult to discover the reason for this ; it is chiefly 

 due to the division of what was previously one subject into two, 

 namely, into anatomy and physiology. This sub-division has 

 been extended to the cell, and, it seems to me, with rather un- 

 fortunate results ; for the separation which, in spite of the many 

 disadvantages which are naturally attached to it, is in many 

 respects a necessity in the investigation of the human body as a 

 whole, is not practicable in the study of cells, and has in reality 

 only brought about the result, that the physiology of the cell has 

 been dogmatically treated as a part of descriptive anatomy, rather 

 than as a science, and that in consequence much that the diligence 

 of scientists has brought to light is barren of results. In this book 

 I have avoided the beaten track, and in order to emphasise this 



