1910.] NATURAL SCIENCES OF PHILADELPHIA. 1 1 



of the intestine from one end to the other. The anterior portions, 

 Nos. 1 to 11, were wholly negative, there being no spores cither in 

 the lumen or in the cells. Beginning with int. 13, however, spores 



were present in the lumen, and they were seen in the cells in int. 

 19, 23, and 25. Their absence from int. 21 is to he credited to the 

 severe exfoliation there present. 



From int. 13, where the spores were first seen in the lumen, there 

 was a rapid increase in their numbers in each successive piece, and 

 in the lumina of int. 23 and 25 they were present in enormous numbers. 

 From this it is evident that it requires but one hour for the ingested 

 spores to reach the extreme posterior end of the small intestine, and 

 as shown both by this and other mice, apparently the great majority 

 of them reach this situation very quickly. While they have also 

 been found in the caecum in very early stages, they evidently do not 

 pass from the small intestine into the caecum as readily as they 

 pass along the small intestine itself. This is evidenced by the fact 

 that in the earlier stages — up to 9 hours or thereabouts — the lasl 

 two or three centimeters of the small intestine always harbor spores 

 free in the lumen. 



There is thus brought about a state of affairs of some interest 

 when the earlier stages of the evolution of the parasites is under 

 consideration. It is evident that the spores pass along the small 

 intestine very rapidly until the posterior end is reached. The 

 length of time required for this stream of spores to pass a given point 

 will obviously vary in the different mice. In those cases where, as 

 a result of prolonged nibbling, the ingested meat reaches the stomach 

 thoroughly comminuted, we may presume that its stay in the stomach 

 is shortened and its movement along the small intestine more rapid. 

 On the other hand, when the meal is swallowed in large pieces, the 

 presumption is that it will remain in the stomach until it is softened 

 and disintegrated, and in consequence its progress along the small 

 intestine will be delayed. Nevertheless, digestion in mice of purely 

 animal matter is rapid, and in general at the end of a few hours spores 

 are scarce in the lumen of the upper and middle portions of the 

 small intestine. If, as a pure guess, we may assume that the stream 

 of spores requires one hour to pass a given point, then the spores 

 within the cells in any particular part of the intestine (except the 

 posterior end) will all have entered the cells within an hour of one 

 another. On the other hand, as we have seen, great numbers of the 

 spores reach the posterior part of the intestine within one hour, and 

 remain there for several hours, as is shown by finding them in this 



