1 84 



REPORT OF THE COMMISSIONERS OF 



observed in the spore. They get into the lymph through the epithelial cells and here 

 develop rapidly into amoeboid forms, especially in the vicinity of the unstriped muscles 

 surrounding the digestive tract. The first indication of this change is a small vacuole 



in the center of the sporozoite (Figure 4, B). This is 

 almost always accompanied by a minute swelling at 

 one end of the organism (Figure 4, B), and the swelling 

 becomes a pseudopodium (Figure 4, C). The amoe- 

 boid condition is then established and in this- state 

 the young parasite penetrates a muscle bundle and 

 takes a position among the fibres. As it changes 

 figure 5.— sporozoites entering muscle from the sporozoite into the amoeboid form, the dense 



cells from the lymph space. Begin- . ' 



ning of the amoeboid stage. Camera homogeneous appearance is lost and it becomes first 



drawing, x 1400 diameters. . , . , r . , T 



vacuolated and then finely reticular in structure. In 

 still later stages the protoplasm becomes densely granular and the reticulum 

 difficult to make out. The parasite in the amoeboid stage frequently reaches a 

 considerable size, although I am not able to say whether the larger forms have 

 been in muscle cells and have emerged preparatory to spore formation or have 

 developed in the lymph. I am inclined to the former alternative because of the 



.N 



Figure 6. — Unstriped muscle fibres from the walla of a pyloric ccecum, containing the adult parasites (P) in the 

 amoeboid stage. JV, JV, nuclei of the muscle fibres. Camera drawing, x 1400 diameters. 



densely granular protoplasm and because the only parasites that I have seen entering 

 the muscle tissues were smaller forms. The largest amoeboid individuals (Figures 4, 

 D, and 7, B, D) measure from eighteen to twenty-five microns, while the sporozoites 

 entering the muscle cells measure only from two to four microns (Figure 5). Here, 



