106 THE PHILOSOPHY OF BIOLOGY 



of wire, and by means of this he has reproduced the 

 phenomena of simple contraction and tetanus. But it 

 remains for future investigation to verify any one of 

 these hypotheses. 



When Huxley published his Physical Basis of Life, 

 probably few physiologists had any doubt that proto- 

 plasm was a definite chemical substance, differing from 

 other organic substances only by its much greater 

 complexity. But in 1880 Reinke and Rodewald 

 published the results of an analysis of the substance of 

 a plant protoplasm and these appear to have demon- 

 strated that the substance was really a mixture of a 

 number of true chemical compounds and was not 

 a single definite one. Now all of these substances 

 might exist apart from protoplasm, and in the lifeless 

 form, and a simple mixture of them could hardly bring 

 forth vital reactions. These results were followed by 

 the morphological study of the cell — the discovery of 

 the architecture of the nucleus, and so on, and so 

 opinion began to turn to the hypothesis that the 

 vital manifestations of protoplasm were the result of 

 its structure. Microscopical examination of the cell 

 appeared to disclose a definite arrangement, the " foam " 

 or " froth " of Butschli, for instance. But, again, it 

 was easity shown that the foam, or alveolar structure 

 of protoplasm was merely the expression of physical 

 differences in the substances composing the cell- 

 stuff — they reduced to phenomena of surface tension 

 and the like. Artificial protoplasm and artificial 

 AmoehcB were made — at least mixtures of olive oil and 

 various other substances were made which simulated 

 many of the phenomena of protoplasm in much the 

 same way as crystalline products may be made which 

 simulate the growth of a plant stem with its branches. 

 For instance, one has only to shake up a little soapy 



