10 PROCEEDINGS OF THE ACADEMY OF [Jan., 



the term "slight" defines those conditions in which epithelial degen- 

 eration is just beginning to be manifest, and "moderate" conditions 

 where the tips of the villi are seriously affected, and "severe" con- 

 ditions where the destructive influence has gone further. 



The data given in the above lists seem to establish the fact that 

 exfoliation of the epithelium is correlated with ingestion of the 

 spores of Sarcosporidia, but they are not consistent amongst them- 

 selves. Thus, mouse 248, a 2-hour stage, is not so badly affected 

 as mouse 246, killed only one hour after feeding, whereas mouse 251, 

 a H-hour stage, shows no exfoliation at all, although in this last case 

 observations were confined to only a small part of the intestine. 



In the cases of Nos. 249 and 261, both 3-hour stages, and No. 247, 

 4-hour, exfoliation is not extensive, while No. 262, 5- to 3-hour, 

 shows a considerable amount near the posterior end of the intestine, 

 as does also No. 250, 5-hour. On the other hand, mouse 253, killed 

 6 hours after feeding, is but slightly affected. In view of the rather 

 contradictory nature of the data, it is impossible to attempt any 

 explanation of the modus operandi of loss of the epithelium. 



Erdmann suggested that the destruction of the epithelium was an 

 adaptation having for its purpose the easier penetration of the 

 spores into the tissues of the mouse. Presumably this destruction 

 is correlated with ingestion of the parasites, but if it be of any value 

 to host or parasite it seems more plausible to regard it as a defensive 

 move on the part of the former. In their attack upon the mouse 

 the parasites first invade the epithelial cells and this they do within 

 the first two or three hours. Obviously, then, the destruction of 

 this epithelium, either before or after penetration by the parasites 

 can only work to their disadvantage. Hence, while it is possible 

 to look upon this exfoliation as an adaptation on the part of the 

 host, there seems no good reason for so doing. It is a matter of 

 observation that exfoliation follows the ingestion of sarcosporidian 

 cysts, but it is also a matter of observation that such ingestion is 

 practically always followed by infection of the muscles. Hence, 

 the exfoliation is obviously not protective. 



The matter is, however, one of minor importance and the data 

 are merely given for what they are worth. 



Evolution of the Parasites in the Cells. . 



The account of the findings in the cells may appropriately be 

 begun with mouse 246, killed one hour after feeding. As indicated 

 in the table on p. 8, slides were prepared from the alternate pieces 



