CHEMICAL ACTIONS: PROTOPLASM 



reconstruct the proteins according to the specific 

 structure of protein which is characteristic of the 

 particular species of organism. Further, we learn 

 from the experiments on precipitin reactions that 

 the morphological position of a species in the 

 system is also physiologically founded. We may 

 suppose that closely related species must also 

 show chemical relations. The chemical mechanism 

 of the precipitin reaction is not yet clear. We can 

 think of the phenomenon mentioned in a foregoing 

 chapter, that two colloids of contrary electric 

 charge flake each other out. Since albuminous 

 substances readily change the kind of electric 

 charge, many opportunities would be given 

 to cause such precipitate reactions. It has been 

 shown without doubt that the precipitin is entirely 

 consumed in the reaction. Therefore we cannot 

 state that any resemblance exists with enzyme 

 reactions. Living cells can even produce specific 

 substances having the properties of proteids 

 which have the power to agglutinate other cells 

 or unicellular organisms such as bacteria. A 

 similar effect is obtained by adding to a culture 

 of typhoid bacteria in the test-tube some of the 

 blood serum of an animal which had been pre- 

 viously treated with typhoid bacteria by in- 

 travenous injection. Flakes of bacteria are 

 formed, between them the liquid becomes quite 

 limpid, and the medium which had been turbid 

 with bacteria shows itself later on quite clear, and 



