ENTAMCEBA HISTOLYTICA 203 



It sometimes happens that the majority of the cysts seen in a specimen 

 of fseces are in the uninucleate condition, while two and four nuclear 

 specimens may be very difficult to find. In other cases the majority of cysts 

 have four nuclei. There seems to be no regularity regarding the stage 

 of development in which cysts are passed, and this is not surprising when 

 it is remembered that the evacuation of the large intestine depends upon 

 the host, and may occur either before or after encystment has commenced. 



The cysts of E. histolytica will remain alive for a considerable time after 

 leaving the body in faecal matter, but if brought into clean water they 

 will survive a much longer period. During this time the chromatoid 

 bodies gradually disappear. When the cysts die, various degenerative 

 appearances become evident, and it is found that the cysts will stain 

 immediately if brought into eosin solution. It appears that eosin solution 

 may be used as a test of the life of a cyst, as also of the free amoebae them- 

 selves. The live cysts or amoebae will not stain immediately, whereas 

 the dead ones will become red at once. This can readily be demonstrated 

 by watching the effect of eosin on cysts before and after heating to a 

 temperature sufficient to kill them. 



In his description of the development of E. histolytica, Schaudinn 

 (1903) described a method of reproduction by bud formation. The 

 nucleus was supposed to give off chromatin material into the cytoplasm 

 in the form of granules, which collected in groups on the surface of the 

 amoebae. Small cytoplasmic buds, each containing a group of chromatin 

 granules, were formed. These buds were described as becoming enclosed 

 in very resistant capsules, forming spores, which were much smaller than 

 the cysts of E. histolytica, as they are now known. Schaudinn claimed 

 to have produced infection in cats by means of these spores after complete 

 drying, a procedure which is known to kill immediately the cysts of 

 E. histolytica. Eecent investigations have failed entirely to confirm 

 Schaudinn's statements, so that it is safe to conclude that the budding 

 process and spore formation as described by him do not take place. 



PATHOGENICITY.— It has usually been assumed that any individual 

 who is harbouring E. histolytica must have definite lesions of the intestinal 

 wall, in the tissue of which the amoebae are living, but though this may 

 be true to a very large extent, the successful culture of the amoebae in 

 tissue-free media suggests that they may sometimes live on the surface 

 of the intestine without giving rise to actual lesions. In some cases the 

 lesions give rise to large quantities of blood and mucus, so that the acute 

 condition of amoebic dysentery results. In the great majority of cases, 

 however, very few, if any, symptoms are noted, so that the infection can 

 only be detected by microscopic examination of the faeces. The fact 

 that in some individuals the symptoms of acute dysentery occur, while 



