440" J. A. GUruth and L. B. Btdl: 



ally fills the cell, which becomes enlarged to three or four times 

 the original diameter, the cytoplasm forming an envelope of the 

 cyst, with the enlarged flattened and elongated cell-nucleus at 

 the edge (Plate LXXIX., Fig. 14). On cessation of multiplication 

 the nuclei gradually become surrounded by protoplasm, and 

 develop into spindle-shaped merozoites (4.3 to 5.5/m, long by 

 2.1 to 2.5/x broad), which, when mature, escape through the 

 attenuated and ruptured cystic cell wall, and may be seen lying 

 free between cells, invading lymph spaces, and even small blood- 

 vessels, and within the lumen of the intestines, these last being 

 the spores observed in the original intestinal smears. Groups 

 of the free spores are to be found within ^he enlarged and con- 

 gested mesenteric lymph gland, noted on post-mortem. 



As to the nature of the body cells invaded by these two dif- 

 ferent parasites, it seems to us that in the case of the large 

 cysts they are epithelial in nature, and in the small "cysts'' 

 leucocytes. With the large cysts in the absence of the very early 

 stages it is impossible to be dogmatic, but the arrangement and 

 the situation, which is never below the line of gland acini, sug- 

 gests a simultaneous invasion of a number of epithelial cells in 

 a duct or acinus of Lieberkiihn, which would account for the 

 grouping and the peripheral distribution of the cell nuclei. In 

 a very few cases we have observed a single cyst at the edge of 

 a villus which also supports this view. 



As in the small "cysts,'' the cells so definitely invaded are 

 certainly not epithelial, for they are always situated within the 

 basement membrane of the villi. Comparing these cells in the 

 very earliest stages of infection with cells within unaffected villi, 

 and with cells in normal villi, there seems to be no doubt that 

 they are mononuclear leucocytes (Plate LXXVIII., Fig. 13). 



Free Spores in Intestine. (Plate LXXIX.). 



Smears of the contents of the whole intestinal canal except 

 those of the rectum, especially those smears made from the 

 material immediately covering the mucous membrane, show enor- 

 mous numbers of spores, evidently those liberated on maturing 

 of the smaller parasites. These spores are much larger than 

 those seen in sections probably owing to the better fixing pre- 



