206 SARCOSPORIDIA. 



as darkh' as the central area of the spore. The cytoplasm at 

 the blunt end tended to be lighter coloured. (b) The other 

 form was distinctly t)t a crescent shape, and in many cases was 

 very definitely crescentic, possessing ])ointed ends, one of which 

 has, as a rule, a little blunter end than the other. The cytoplasm 

 generally stained a very pale violet colour, in marked contradis- 

 tinction to the deep blue of the stout spores ; at or near the 

 centre were grouped violet-colom-ed granules. In some in- 

 stances the granules were found rather siiattered in the spore 

 cytoplasm. As regard to size, there does not seem to be much 

 difference. 



According to McGowan ( 1914). if the sporozoites or sickles 

 be emulsified in a to i)er cent, acetic acid solution, deeply tinged 

 with thiom'n IjIuc, a nuiu))ei' i»f imjjortant points can. be observed. 

 In tlie hrst i)lace it will l)e ^-een that a definite capsule surrounds 

 the i)rt)t()plasm of the sickle. Further, b}' the cdjove method 

 the unstained hyaline ca])sule is easily seen by contrast with the 

 stained protoplasm of the ])arasite. Especially is this so at the 

 sharp end of the sporozoite, where a V-shaped space is left 

 between the rounded end of the protoplasm and the capsule. 



Pdssip.li-: I)K\'KLorME.\'j' Stacks of the Sarcocyst. 



Theobald Smith found that when muscular tissue contain- 

 ing matured sporozoites was fed to mice, no evidence of any 

 invasion of the muscular tissue could be observed until the forty- 

 iifth (lay. when the smallest parasites were detected. These 

 Avere fusiform in shape, consisting of a delicate structureless 

 membrane, with hyaline contents. As the ])arasite grows and 

 elongates, its substance becomes divided into a number of fusi- 

 form bodies whose long axes are nearly parallel to that of the 

 mother tube. This |)rimary stage of the fusiform bodies is 

 soon followed by another, seen first in the central ])art of the 

 tube. Here the parasite becomes broader and more opaque. 

 In about seventy days after feeding the parasites enter the 

 stage of spore and sporozoite formation, the substance of the 

 jjarasite being made up of relatively large roundish or polyhe- 

 dral masses of a finely granular appearance. These sporoblasts 

 soon break up into the sporozoites, probably eight from each 

 sporoblai^t. Negri was able to infect guinea-pigs with the sar- 

 cocyst of the mouse by feeding them with infected mouse flesh, 

 and found that in the guinea-pig the parasite appeared with 

 different characters from those which it presents in the mouse. 

 Erdmann infected mice with the sarcocyst occurring in sheep. 

 According to Erdmann. the spore germinates in the intestines 

 of the new host, and the first act of the spore is to liberate a 

 toxin, W'hich causes the adjacent epithelium of the intestines to 

 be throw'n off. At the same time Amcebula is set free from 

 the spore, and in virtue of the toxin liberated by the spore, 

 the Amoebula is able to penetrate into the lymph spaces of the 

 submucous coat and establish itself there ; sinmltaneously with 

 the secretion of the toxin the metachromatic grains disappear, 

 and it is suggested that the toxin is contained in these granules. 



