AMOEBA PROTEUS 49 



stances which, as soluble materials, are then taken into the 

 body protoplasm of the organism ; the food particles are said 

 to be digested. 



When the protein food is thus digested it is only prepared for 

 the first stages of protoplasm re-building, and many more steps 

 must be taken before the essential elements are added to the 

 protoplasmic molecules. These further steps are generally 

 included under the comprehensive term, assimilation, and their 

 exact nature is hidden in the deepest obscurity. Little by little 

 chemical research is throwing light on the processes, so that we 

 have now a basis for working hypotheses as to the manner in 

 which protoplasmic molecules are built up. We now know that 

 cells in all kinds of tissue possess chemical properties hitherto 

 unsuspected. These have to do, in the main, with enzymes 

 which act upon the partially broken down food matters and 

 cause their disintegration into finer particles, until they are 

 prepared for anchorage in the protoplasmic molecules, and be- 

 gin the series of integrations and disintegrations characteristic 

 of vital processes. It has been found by experiment that 

 portions of the cell without a nucleus cannot form such enzymes, 

 and the conclusion is drawn that these vital activities are de- 

 pendent upon substances derived from the chromatin. It was 

 largely through experiments in cutting minute forms like 

 Amoeba that this discovery was made. Nusbaum, Hofer, 

 Verworn and others found that if an amoeba is cut in two pieces 

 with a scalpel, both parts would continue to live for some days 

 but one would die ultimately, while the other part, containing 

 a nucleus, would continue to live and multiply indefinitely. 

 The portion without a nucleus is unable to digest and assimi- 

 late food, or even to capture it. 



Thus while the exact processes of assimilation are unknown 

 in amoeba, it is quite probable that the finer changes are carried 

 on in the same way as with cells in higher animals, that is, 

 through the agency of enzymes. These act in a linked series, 

 the product of one chemical action furnishing the material for 



