76 ENCYSTMENT AND EXCYSTATION OF AMCEBA 



of the dead bodies of bacteria or of certain soluble 

 products of the growth of living bacteria. 



These products are probably of the nature of 

 ferments, as they are destroyed by boiling but not 

 by chloroform. 



The action of these substances is increased if an 

 augmentor such as choline is present. 



Unboiled pepsin solutions will produce excysta- 

 tion in a limited number of the cysts, while boiled 

 solutions are ineffective. Normal horse serum 

 contains substances which will cause excystation. 



Growth and reproduction. The food of an 

 amoeba under natural conditions consists of living 

 bacteria. These can be replaced in artificial cultures 

 by dead bacteria provided there are present in 

 addition certain substances which are destroyed by 

 boiling and which are probably of the nature of 

 ferments. 



Multiplication does not, however, take place unless 

 an auxetic such as tyrosin or creatine is present, 

 and we think this may act by enabling the ferment 

 to influence the chromatin of the cell in some 

 manner not yet understood. 



The " augmenting " action of a kinetic may then 

 be due to the activation of the process originated 

 by the combined action of the auxetic and the 

 ferment. 



The results of the above experiments on amoebae 

 have prompted us to undertake an investigation 

 into the action of ferments, in the presence of 

 various combinations of auxetics and kinetics, on 

 the reproduction of individual human and other 

 cells. 



