ENTAMOEBA HISTOLYTICA 57 



however, the cysts hatched, and each Hberated a 4-nucleate amoeba. 

 These amoebae passed down the intestine with the gut-contents, and 

 were found in the large bowel and the evacuations. According to 

 Chatton the newly hatched amoebae actively ingest bacteria, become 

 vacuolated, and their four nuclei become clumped together. Further 

 development was not seen. 



Chatton believes his observations to indicate that the cysts of 

 E. histolytica normally hatch in the small intestine, liberating undivided 

 4-nucleate amoebae, which first live upon bacteria and then pass on and 

 establish themselves in the tissues of tlie large bowel. He interprets the 

 ingestion of bacteria in a phylogenetic sense — as an indication that this 

 species was primitively a commensal, like E. coli, before it took to preying 

 upon the tissues. I do not share this view. I think it more probable 

 that his amoebae were degenerate, and invaded by bacteria.* The fact 

 that they were vacuolated supports this interpretation ; for vacuolation is 

 one of the first signs of degeneration in E. histolytica. The fact that the 

 nuclei were later found to be agglomerated still further supports it ; for 

 agglomeration of the nuclei is often seen in multinucleate protozoa during 

 degeneration.! It is, of course, impossible to know whether the cats in 

 which these amoebae were found would have become infected if they 

 had not been killed : but Chatton states that none of his controls became 

 infected. t It seems probable, therefore, that the cats which were killed 

 would also have remained uninfected. I am thus inclined to think that 

 the cysts, in these experiments, hatched in an abnormal manner, and the 

 amoebae afterwards degenerated and gradually died. The intestine of 

 the cat was sufficiently like that of man — their normal environment for 

 development — to enable them to emerge ; but it was not sufficiently like 

 the human intestine to enable them to develop. The experiments 

 support the view, which is at present the only probable one, that the 

 cysts hatch in the small intestine. But they by no means prove that 

 the cj'st normally liberates a 4-nucIeate amoeba in man ; or, if it does,, 

 that its later development is similar to that observed in the cat. Chatton 

 himself says that " the incomplete development in the cat is due to the cat 

 being not a normal host of the amoeba." 



Ujihara (1914) had previously stated that the cyst wall of E. histolytica 

 is soluble in trypsin, but almost insoluble in gastric juice. This seemed 

 to indicate the small intestine as the place where the cysts normally 

 hatch : and Penfold, Woodcock, and Drew (1916) have stated that they 

 were able to cauxe cysts to hatch by placing them in liquor pancreaticus 

 (Benger), — in which, however, " only a small proportion excyst." They 

 say : " We have tried pepsin, in an acid medium, bile, and pancreatic 

 extract, either alone, consecutively, or together, as appeared indicated, § 

 but the only success we have had has been with pancreatic extract used 

 alone." They observed the emergence of a single amoeba from the cyst, 



* See p. 62. 



t For instance in Trichosphaerium and Actinosphaerium. 



X He Says : " None of the cats not sacrificed in my experiments has contracted 

 dysentery as a result of ingestion of the cysts." 



§ It would be interesting to know the " indications " for acting upon cysts with a 

 mixture of trypsin, in acid solution, and alkaline pancreatic juice. I cannot help think- 

 ing that an amoeba — even if quite willing to emerge — would be as much perplexed by 

 being placed in such a mixture as I am in trying to conceive the indications for its use. 



