MORBID ANATOMY 387 



assuming that the microparasites are conveyed by the blood 

 directly from the diseased ceca into the liver and there de- 

 posited in different places, where they begin to multiply and 

 spread in all directions. In this way they form the spherical 

 foci of disease which appear as circles on the surface of the 

 liver. This theory is borne out by the results of the micro- 

 scopic examination. 



In sections of hardened tissue from the liver in which the 

 disease has but recently begun, the affected regions are invaded 

 by large numbers of protozoa which occupy a kind of reticu- 

 lum formed probably from the connective tissue stroma. The 

 liver cells have partially or wholly disappeared from these foci. 

 The border of the necrotic tissue is surrounded by a zone of 

 giant cells. The parasites occupy the meshes of the tissue 

 either singly or in groups. The reticulum is provided with a 

 small number of nuclei, some of which are closely applied to 

 and curved partly around the parasite. The blood vessels are 

 usually much dilated and filled with red corpuscles. 



The yellow masses observed with the naked eye in the 

 surface spots are shown to be patches of an amorphous sub- 

 stance which take nuclear stains very feebly, the aniline colors 

 not at all. This may be described as a coarse network in the 

 meshes of which small cells, and very rarely parasites, are 

 seen. This substance is assumed to be the result of coagula- 

 tion necrosis of the liver cells by which they have lost their 

 nuclei and have become fused into a formless mass. It is 

 probable that the plugging of blood vessels in the liver by 

 parasites carried from the cecum is the cause of the necrosis, 

 since such plugs or thrombi are not uncommon in sections of 

 the diseased areas. 



With the appearance of the microparasites regenerative 

 changes begin at once which complicate the process. We 

 have at the outset an active multiplication of the micropara- 

 sites which take the place of the original liver tissue and a 

 process of coagulation necrosis going on at the same time. 

 Soon multinucleated (giant) cells appear. Not infrequently 

 they are grouped around what appears to be a plugged 



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