320 INFECTIOUS ENTERO-HEPATITIS 
late 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 inclosed 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 within the spaces, by virtue of 
which the mucous membrane is thickened. In this early stage of 
invasion the epithelium, both of the tubules and of the surface, 
remains unaffected. 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 coat. 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 inflammation finally extends to the serous 
covering, where the blood vessels become greatly dilated and give the 
cecum a congested appearance. In cases of ordinary severity the 
wall of the cecum which is not more than 0.2 to 0.5 mm. thick normally 
becomes 2 to 3 mm. thick. 
With the progress of the disease the mucous membrane may be 
shed and a coagulable fluid poured out into the cecum. In some 
cases it appears in isolated masses, which adhere to certain spots of the 
mucous membrane. In others, this exudate fills the entire tube with 
a yellowish-white mass, built up in concentric layers consisting of a 
mixture of blood corpuscles, fibrin and small round cells in variable 
proportion. 
In the further progress of the local disease it is not improbable that 
bacteria are also concerned. The exudate contains immense numbers 
of them and the denuded mucosa furnishes a favorable place of entry. 
It is otherwise difficult to explain the continued increase in thickness 
of the walls of the cecum after the mucous membrane has been shed. 
This continued increase in thickness is due to an extensive infiltration 
of small round cells and the presence of some giant cells. Parasites 
in this advanced stage are scarce and usually recognizable only as 
vacuole-like bodies within the giant cells. 
The thickening of the wall is associated in some cases with an 
extension of the inflammation to the contiguous wall of the intestine, 
which becomes firmly attached to the cecum. Yellowish exudates are 
sometimes found outside of the diseased cecum on its serous covering 
