254 THE PROTOZOA 



not; 



course instead of the vegetative nucleus of tetragena type one may 

 in chronic cases or in convalescence come across the four nuclei cysts 

 of E. tetragena. 



Animal experimentation upon kittens with E. coli by Schaudinn, Craig and 

 Wenyon have been unsuccessful as to production of dysenteric manifestations. On 

 the other hand all of these experimenters produced typical lesions and dysenteric 

 manifestations in kittens injected rectally or fed with material containing patho- 

 genic amoebae. 



Wenyon produced a liver abscess in one of his experiments. In man the dislodg- 

 ment of amoebae containing material from amoebic intestinal ulcerations and the 

 plugging of the portal capillaries by such emboli gives us the starting-point of a liver 

 abscess. The exciting cause is Entamceba histolytica which in the liver continues 

 the same production of a gelatinous necrosis as is carried on in the submucosa of the 

 large intestine or appendix. 



Darling has been so successful in his experimental work with kittens that he 

 compares the colon of a kitten to a test-tube and suggests the procedure of rectal 

 injections of material containing amoebae as a means of differentiating the two human 

 amoebae. 



On the other hand Walker was unable to infect kittens and monkeys with material 

 containing pathogenic amoebae and he makes the statement that such failures would 

 indicate the greater susceptibility of man to infection, as he was able to infect 17 

 out of 20 men with one feeding of such material. 



Recently Walker and Sellards have published a most important 

 paper. 



The experiments were made in men who had been under observation for years 

 at Bilibid Prison, whose food was cooked and the water they drank distilled. More- 

 over, there were complete records of examination for intestinal parasites, including 

 entamcebae. They were under complete control and the existence or possibility of 

 natural infection with amoebae was reduced to a minimum. All the men fed patho- 

 genic amoebae were volunteers and each signed, in his native dialect, an agreement to 

 the conditions of the experiment. 



The first series of experiments was with cultural amoebae, in order to refute state- 

 ments that amoebae cultivated from water or other nonparasitic sources, as well 

 as from dysenteric stools, are capable of living in man parasitically or of producing 

 dysenteric symptoms. Twenty feeding experiments were made by Walker and 

 Sellards with cultures of amoebae without the development in a single instance of 

 dysentery or the finding of such amoebae in the stools upon microscopical examina- 

 tion. In 13 cases they recovered the amoebae in cultures from the feces from the 

 first to the sixth day, but never afterward. They stated definitely that cultural 

 amoebae are nonpathogenic. 



The next experiments were with Entamoeba coli. In the 20 cases fed with material 

 containing Entamaba coli there was a uniform failure to recover them culturally and 

 in no instance was dysentery produced. Seventeen became parasitized as the result 

 of a single feeding in from one to eleven days, the entamcebae being found in the 

 stools and persisting in their appearance in the stools for extended periods. They 



