ENTAMOEBA HISTOLYTICA 65 



individual will be found to have an abnormal nucleus, and to show other 

 typical signs of degeneration. Fig. 81 (PI. V) depicts a common type of 

 precystic amoeba from a stale stool. The structure of its nucleus at once 

 stamps it as a dying or dead organism. 



E. histolytica may also — though this is very rare — be pai^asitized by- 

 bacteria. I have made a careful study of three such infections, and have 

 satisfied myself of the correctness of the observations. I do not know 

 whether the parasitic bacteria occur in the tissue-invading forms within 

 the intestinal ulcers : but they are ceitainly present in the precystic 

 amoebae. Fig. 83 (PI. V) shows one of these from the case which I 

 studied in the greatest detail. The patient in whom this infection 

 occurred was a convalescent carrier of E. histolytica, and the amoebae 

 were obtained by the administration of a saline purgative. The prepara- 

 tions were fixed almost immediately after the amoebae left their host, so 

 that a post mortem invasion of their protoplasm by bacteria can, I think, 

 be excluded. A large percentage of the amoebae, in this instance, 

 contained the micro-organisms shown. They were also present in the 

 eysts (fig. 84, PI. V) ; but almost all such infected cysts were uninucleate. 

 There were uninfected amoebae also, and normal uninfected cysts con- 

 taining I, 2, or 4 nuclei. It thus seems highly probable that the parasitic 

 bacteria in the precystic amoebae did not prevent encystation, but 

 arrested the development of the cysts at the uninucleate stage. The 

 bacteria were easily visible inside the living uninucleate cysts ; and when 

 these were kept they rapidly degenerated — the bacteria apparently 

 increasing in numbers within the cysts, which finally contained merely 

 disintegrated protoplasm and many bacteria in active Brownian move- 

 ment. All the parasitized amoebae and cysts showed more or less 

 degenerate nuclei (cf. figs. 83 and 84). 



Another case of the same sort I studied with Dr. A. C. Stevenson,, 

 who kindly permits me to record our observations. This patient also 

 was a convalescent carrier, and was under observation for about six 

 months, during which time his stools were examined repeatedly. They 

 almost always contained numerous cysts of £. histolytica ; and these 

 were almost invariably uninucleate, and parasitized by bacteria (fig. 85,. 

 Pi. V). They frequently contained chromatoid bodies also, but these 

 were generally large and easily distinguishable from the bacterial in- 

 clusions. Binucleale cysts were very rare, and 4-nucleate cysts were 

 never found. As in the preceding case, the cysts died very rapidly out- 

 side the body on every occasion when they were kept under observation. 

 We came to the conclusion that the cysts were infected with a parasitic 

 micro-organism which inhibited their development, but we did not 

 obtain amoebae from this case. Infected cysts were passed by this 

 patient for about five months, during which time he was unsuccessfully 

 treated several times. At each relapse after treatment he passed infected 

 uninucleate cysts once more. As only degenerate uninucleate cysts 

 occurred, we were often in doubt as to whether many of them were 

 really cysts of E. coli. After a final thorough course of treatment, how- 

 ever, with emetine bismuth iodide, all the cysts vanished from the stools 

 and never reappeared subsequently, although the examinations were 

 contmued over a considerable period. 



The first patient was also treated with emetine bismuth iodide, and 

 likewise cured of his infection. Both cases were, I think, undoubtedly 

 infected with a strain of E. histolytica which was itself infected with a 



