56 ENCYSTMENT AND EXCYSTATION OF AMGEBA 



malignant tumour a sort of balance, just as in 

 the case of an amoeba in relation to the bacterial 

 products to which it is exposed, and the chemical 

 conditions present as regards the quantity and 

 quality of auxetics and kinetics may possibly 

 determine the question as to whether the tumour 

 will continue to grow, or will break down and 

 ulcerate. 



THE PHENOMENON OF "EXCYSTATION" 



The experiments on this subject were under- 

 taken to find out the nature of the substances 

 produced by bacteria in the environment of amoeba 

 cysts, which we believed to be responsible for the 

 dissolution of the cyst wall and the liberation of 

 the free amceba. 



Theoretical Considerations. Various suggestions 

 have been made from time to time to explain why 

 an encysted organism, such as an amceba, develops 

 into the free living form on transferring it to a 

 fresh medium. The popular expression is that 

 the amoeba escapes when conditions are again 

 suitable for its existence in the free form, in which 

 case the employment of such a phrase obviously 

 implies that these conditions must form the 

 starting-point in the process, whatever may be 

 the actual changes taking place within the cyst. 

 The expression " suitable conditions " is capable 

 of two interpretations as follows : Firstly, it may 

 be said that the amceba has been removed from the 

 presence of those substances which have brought 

 about the encystment, and that excystation will 

 accordingly now take place. If one were to accept 



