422 SCIENTIFIC THOUGHT. 



literature, to have placed it at the entrance of his text- 

 book of physiology, and thus to have given the student 

 a somewhat more detailed description of the elementary 

 functions of living matter than was afforded by the older 

 term " vortex," employed by Cuvier. 

 33. These merits of Schwann, which attach more to the 



"Metabol- 

 ism." conception of " metabolism " than to that of the cell, 



are not reduced by our having to state that the latter 

 conception has been entirely changed since his time. 

 The cell of to-day is not the cell as Schwann conceived 

 it. Of the pretty clearly defined structure or organ- 

 isation of that biologist, with its wall (membrane), 

 its kernel (nucleus), and its fluid contents (cell sap), 

 nothing; has remained but the cell contents, termed 

 protoplasm by von Mohl ; and the living process can no 

 longer be considered as the function of a well-defined 

 organ or machine. It is rather the fundamental property 

 of an almost homogeneous substance, the mass of proto- 

 plasm, in which the kernel is the only recognisable 

 differentiated portion. The immediate eft'ect of this de- 

 structive analysis of the early conception of the cell was 

 to destroy the idea that the living processes carried on in 

 any special cell or organ are a result of its organisation, 

 as the function of an apparatus is dependent upon the 

 arrangement and combination of its parts. It has pro- 

 moted the view that — for our understanding at least — 

 the first thing to learn is the nature of the processes 

 themselves. We have to look upon the visible structure 

 of special cells and organs merely as " mechanical con- 

 trivances, serving only to modify in special ways the 

 results of the exercise of these fundamental activities. 



