SPOKOZOA. 191 



though the general state of health remained the same, and showed no 

 further abnormal phenomena. Since the elapse of two weeks resulted 

 in no further change, and the excrement remained firm and normal in 

 spite of the associated mucus, the dog was killed eighteen days after 

 the first injection. On examination the mucous membrane of the 

 rectum was found in some places reddened, irregularly swollen, covered 

 with viscous blood-stained mucus, and superficially ulcerated in three 

 places. The ulcers were roundish, of 4 to 7 mm. in size, and sur- 

 rounded by swollen and exceedingly hyperaemic mucous membrane. 

 Their base was irregular, and had a dark red appearance. The sub- 

 mucosa below was hypersemic, swollen, moist, and turbid. The mucus 

 in the rectum and in the ulcers was thickly crowded with Amoebae, 

 which differed in no respect from the injected parasites. The mucous 

 membrane of the large intestine was normal, nor did the other organs 

 exhibit any pathological character. 



This experiment proves at least that these Am&bce, if abundantly 

 developed in the intestine, may give rise to violent irritation of the 

 mucous membrane, and cause not only hyperaemia and increased 

 formation of mucus, but also an intense inflammation, sometimes 

 aggravated by ulceration. 



CLASS II. SPOEOZOA. 



[Davaine, " Leons sur les Sporozoaires :" Paris, 1884. R. L.] 



Unicellular parasites of definite form, without pseudopodia or cilia, 

 but covered by a smooth, more or less firm, cuticle. At the anterior end 

 there is not unfrequently an organ of attachment, like a proboscis or 

 cushion. Their movements are inconspicuous, worm-like, or slightly amoe- 

 boid. They live wholly as parasites, and receive their food by endosmosis. 

 Reproduction takes place by more or less hard-shelled spores (Pseudo- 

 navicellce, Psorospermice), which are formed in the interior of the adult, 

 sometimes in very great numbers. Occasionally they appear gradually, 

 but more often simultaneously, and then after the attainment of maturity 

 and encapsulation. In these spores there develop, sooner or later, a 

 varying but usually small number of sickle-shaped bodies, which, after 

 creeping out, become new parasites. In other cases the contents of the spore 

 are collected in a single amoeboid embryo. 



The most familiar examples of these Protozoa are the Gregarines 

 (Fig. 95), which stand highest in their organisation and functional 

 activity, and indeed represent a special group. They are, so far 

 as we know, parasitic only in invertebrates, especially in insects and 



