DISTRIBUTION OF THE AMCEB^E 539 



Both organisms have now been shown to pass into a resting 

 stage with formation of cysts, the character and mode of forma- 

 tion of which are markedly different in the two cases. The cyst 

 formation of the entamoeba histolytica is specially seen when the 

 disease is in process of cure and the stools are beginning to have 

 a less fluid character. In the earliest stage of the change the 

 nuclear membrane becomes broader and fades into the proto- 

 plasm, whilst the chromatin becomes dispersed through the 

 entoplasm in the form of small chromidia. Buds then form 

 on the surface and into these some of the chromatin passes. 

 Around these buds concentric striation can be seen, and then 

 a hyaline cyst wall is formed, which is highly refractile in 

 character. The cyst then becomes separated from the rest of the 

 cell. Several cysts which measure 2-7 p in diameter may be 

 formed from the same amoeba, and the remnant of the cell under- 

 goes disintegration. These cysts, as will be shown below, repre- 

 sent a resting stage with high powers of resistance to external 

 agencies, and are concerned in producing infection of another 

 subject. The cellular changes in the encysting of the entamceba 

 coli have also been worked out by Schaudinn. They are of 

 a somewhat complicated character, involving the formation 

 of reduction bodies and copulation of nuclei, but the ultimate 

 result is the formation of a fairly large cyst, which contains 

 eight small cells. The process of cyst formation accordingly in 

 the two organisms is of a widely different character. 



Cultivation. Various attempts have been made to cultivate 

 the amoeba of dysentery, and Kartulis considered that he obtained 

 growth in straw infusions. Recently Lesage has announced that 

 he has obtained cultures on plates of agar which had been 

 washed in water for eight days. Both the vegetative and the 

 cystic forms were used for inoculation. In some cases a growth 

 of a colon bacillus was made on the agar and afterwards removed, 

 this procedure interfering with the development of such bacilli 

 present in the material used for inoculation. The plates were 

 kept in the sloped position, and the inoculations were made in 

 the lower part ; the amoebae moved to the upper part, where they 

 were got in pure condition. He succeeded in obtaining cultures 

 in seven out of thirty cases, and in some instances cultivated the 

 organisms for more than sixty generations. The amoebae multi- 

 plied by simple amitotic division, and in certain cases produced 

 small cysts. These cysts, as described and figured by him, 

 correspond in all important respects with the changes observed 

 by Schaudinn in dysenteric stools. 



Distribution of the Amrebae. As already stated, they are 



