82 A SCIENTIFIC APPROACH 



common salt for 24 hours a peculiar culture grew, living 

 cells were formed which grew, divided and manifested other 

 features characteristic of life. This work was obviously very 

 amateurish and is certainly of no real importance. It cannot, 

 however, be regarded as an accidental happening or a mere 

 curiosity. It could only have been done under the influence 

 of the mechanistic outlook which we have already discussed. 

 According to this view, the simplest living things could 

 suddenly crystallise out from lifeless matter. The only 

 requirements for this were various more or less specific 

 unknown forces which effected this sort of transformation of 

 substances into living things. M. Kuckuck attributed such 

 effects to radioactive phenomena, which were still poorly 

 understood at that time. 



Another well-known German scientist of the end of last 

 century, E. Pfluger,^* approached the subject under discus- 

 sion in a different way from Haeckel. He sought the cause 

 of the emergence of life in the materials from which the 

 organisms were to emerge as well as in the peculiarities of 

 the external conditions. In his analysis of the problem he 

 started out from the properties of the chemical substance 

 protein, a substance which he associated inextricably with 

 the existence of living processes. Pfliiger considered that 

 there are present in organisms two radically different cate- 

 gories of protein, the reserve protein which was ' dead ' and 

 the protein of the protoplasm which was ' living '. In the 

 former category he included such substances as the whites 

 of eggs and the protein stores of seeds, etc. These proteins 

 appeared to be very stable, chemically inert substances. In 

 the absence of micro-organisms they may be preserved for 

 an indefinitely long time without undergoing any important 

 changes. The ' living ' protein of the protoplasm, on the 

 other hand, seems to be very unstable. Pfliiger held that this 

 instability formed the basis for the chemical transformations 

 which proceed within the living cell. 



In all living things disintegration of proteins takes place. 

 Pflriger attributed this to various special chemical groups 

 in the composition of ' living ' protein. In particular, he 

 thought that ' living ' protein must have the power to oxidise 

 itself by using the oxygen of the air. This follows from the 



