178 THE STORY OF THE LIVING MACHINE. 



toplasm, and must base our understanding of its 

 properties upon its structure. 



It is proper to state that there are still some 

 biologists who insist that the ultimate explanation 

 of protoplasm is purely chemical and that life phe- 

 nomena may be manifested in mixtures of com- 

 pounds that are purely physical mixtures and not 

 machines. It is claimed that much of this cell 

 structure described above is due to imperfection 

 in microscopic methods and does not really exist 

 in living protoplasm, while the marvellous activi- 

 ties described are found only in the highly organ- 

 ized cell, but do not belong to simple protoplasm. 

 It is claimed that simple protoplasm consists of a 

 physical mixture of two different compounds 

 which form a foam when thus mixed, and that 

 much of the described structure of protoplasm is 

 only the appearance of this foam. This concep- 

 tion is certainly not the prevalent one to-day ; and 

 even if it should be the proper one, it would still 

 leave the cell as an extremely complicated ma- 

 chine. Under any view the cell is a mechanism 

 and must be resolved into subordinate parts. 

 It may be uncertain whether these subordinate 

 parts are to be regarded simply as chemical com- 

 pounds physically mixed, or as smaller units each 

 of which is a smaller mechanism. At all events, 

 at the present time we know of no such simple 

 protoplasm capable of living activities apart from 

 machinery, and the problem of explaining life, 

 even in the simplest form known, remains the 

 problem of explaining a mechanism. 



The Origin of the Cell Machine. We have thus 

 set before us another problem, which is after all 

 the fundamental one, namely, to ask whether 

 we can tell anything of nature's method of build- 



