THE PRESENT POSITION OF CELL-THEORY. 103 



in the sense in which I am using it, for the biophor or 

 ultimate vital unit is held to be an aggregate of chemical 

 molecules ; the constitution attributed to it is that it is made 

 up of many different kinds of molecules, just as a molecule 

 may be composed of several different kinds of atoms. I shall 

 have to refer aram to the difficulties which still remain if 

 we accept the hypothesis that a group of different molecules 

 is able to exhibit the vital functions which are necessarily 

 attributed to a biophor. Before proceeding to criticism I 

 must try to give as fairly as I can the grounds for believing 

 in the existence of biophors. To put the matter as briefly 

 as possible, the theories of ultimate vital units are the resuh 

 of attempts to make a mental analysis of living substance 

 Chemical analysis is impossible, for in the process the 

 living substance is destroyed as such and becomes dead 

 substance, possessed of different and much less important 

 properties. One fact of great importance, however, is 

 learnt from chemical analysis, and it was appreciated by 

 Schwann, namely, that, to use his original words, "the 

 elementary materials of organic nature are not different 

 from those of the inorganic kingdom " ; hence it has been 

 inferred, with all reason, that the powers of organic nature 

 are essentially the same as those of inorganic nature, and 

 are established by the very existence of matter. It is only 

 necessary to mention this because there has recently been 

 a tendency in some quarters to call in the assistance of some 

 mysterious " vital force " ; a tendency begotten no doubt by 

 the apparent futility of all attempts to find an explanation 

 on mechanical and chemical principles of the fundamental 

 powers of organic nature, assimilation and metabolism. 

 This, however, need not detain us ; we have to consider 

 the process of reasoning which, in default of assistance 

 from chemical analysis, has led so many distinguished 

 observers and thinkers to analyse the cell into other com- 

 ponents, and those again into others of a lower grade, 

 until the biophor, the smallest particle of possible life, is 

 reached. 



The weightiest reason which I have been able to dis- 



