2.S8 



INFECTIOUS ENTERO-HEPATITIS 



thickening of the wall is the result of 

 several processes — the multiplication 

 of the parasites, the increase of the 

 normal tissue elements and later on 

 the accumulation of masses of small 

 cells and some giant cells. 



In the early stages of the inva- 

 sion, the adenoid tissue between the 

 tubules and in the submucosa be- 

 comes greath' increased owing to the 

 presence of large numbers of micro- 

 parasites of round or slightly oval 

 outline and from 6 to io/< in diam- 

 eter which stimulate the proliferation 

 of the tissue cells. Numerous mitoses 

 have been seen in this stage. The 

 parasites seem to occupy the meshes 

 of the adenoid tissue either singly 

 or in groups or nests. In these 

 meshes they are soon enveloped in 

 cells acting as phagocytes, so that the 

 appearance of an intracellular habitat 

 of the parasites is suggested. 



The presence of the parasites in 

 this reticulum probably stimulates also 

 the accumulation of lymph cells with- 

 in the spaces, in virtue of which the 

 mucous membrane is thickened. In 

 this early stage of invasion the epi- 

 thelium, both of the tubules and of the surface, remains unaf- 

 fected. The parasites do not invade the epithelium at any time. 

 As the disease progresses there is a continued increase in 

 cellular elements of the mucous and submucous coats and a 

 gradual invasion of the muscular coats. Here the bundles of 

 fibers of the circular coat are thrust apart by masses of cells, 

 so that this coat also becomes greatly thickened. The inflam- 

 mation finally extends to the serous covering, where the blood 

 vessels become greatly dilated and give the caecum a congested 



Fig. 64. Caeca; a 

 and b are diseased areas ; 

 c, section of thickened 

 ivall. 



