OF THE ALIMENTARY TRACT 19 



In general the process of encystment has been 

 evolved by the individual species as best suited to 

 their needs, some for reproduction, some for protec- 

 tion in unfavorable environment and reproduction, 

 some purely for protection, while some are not de- 

 pendent upon such a change for either protective 

 or reproduction purposes and do not encyst. 



Neither is it definitely known what leads the en- 

 closed organism to escape from its cyst when it 

 reaches a favorable environment for its further ac- 

 tivity. It has long been assumed that the digestive 

 juices of the alimentary tract cause dissolution of the 

 cyst and allow the imprisoned parasite to escape. 

 It is possible, however, for these same organisms to 

 escape and continue their activities without such 

 digestive action on the exterior, as witness the cul- 

 tures which may now be grown from cysts of some of 

 these organisms. It seems, therefore, that their es- 

 cape is due to their own ''digestive" influences upon 

 the shell which they have formed, some forms leaving 

 a pore of more easily dissolved material through which 

 they may escape. 



In the writer's laboratory notes of 1922, before 

 the recent reports of cultivation of various amoebae 

 of man, occurs the record of attempts to grow man's 

 intestinal amoebae in a serum salt solution mixture 

 similar to some which have since been reported as 

 suitable for such culture work. It was observed that 

 after 24 hours incubation at 37 °C. cysts were empty. 

 Free amoebae were found but transplantation was 



