150 BOWMAN. 



lying in tlie necrotic tissue and a few in the mucosa, the largest number being 

 in the submucosa. Here they are seen in nests in the blood vessels and in the 

 surrounding tissue; and they again may be demonstrated in sections cut through 

 apparently normal portions of the gut at some distance from any ulcer. 



SUMMARY. 



During the past three years I have seen ten cases of infection with Ba- 

 lantidium coli, although during the past eight months balantidia have been 

 found in the faeces of 16 patients in Bilibid Prison hospital. Two of the 

 ten cases terminated fatally, but the others have had no symptoms other 

 than an occasional diarrhoea. Even in the severe infections, the diarrhoea 

 was more or less intermittent in character, the parasites being found in 

 the faeces only during these attacks. This phenomenon might be ex- 

 plained in the following manner: The organisms, moving along in the 

 submucosa, become so numerous as sometimes to form "nests" from 

 which low inflammations develop, and which, proceeding to ulceration, 

 cause erosion of the mucosa and set free the balantidia. (See PL II, 

 fig. 1.) At this time the organisms are found in the faeces. In some 

 areas the blood-vessels appear practically to be occluded by the number 

 of balantidia present and this fact in itself is sufficient to initiate an 

 inflammatory jDrocess by lowering the tissue resistance. 



The possibility that the parasite may carry bacteria and thus cause an 

 inflammatory reaction has been suggested. I have invariably found that 

 the cellular infiltration which is present around the organisms situated 

 beneath the unbroken mucosa practically consists of lymphoid cells and a 

 few eosinophiles (PI. II, figs. 1 and 2), very few polymorphonuclear leu- 

 cocytes being present. This fact in itself seems to show conclusively 

 that the primary inflammation is not caused by bacteria. However, the 

 necrotic material covering the ulcers is composed largely of leucocytes 

 and there is no doubt that the terminal, acute ulceration begun by Balan- 

 tidiuni coli in the underlying tissue is due to a great extent to the entrance 

 of intestinal bacteria. 



The manner of primary invasion is not determined. It has not been 

 established whether the mucosa must be injured before the parasites can 

 enter or whether they in themselves are capable of piercing the uninjured 

 mucosa. A third possibility is that they liberate a cytolytic ferment 

 which causes the injury. However, once an entrance is gained, multi- 

 plication rapidly takes place and it is only a matter of time until the 

 entire colon may be infected. 



I have examined many preparations, both fresh and stained and fixed 

 in the tissue, but have never seen any distinct evidence of conjugation 

 taking place between two organisms. The balantidia may be seen in 

 groups and in pairs closely attached, but showing no nuclear cytoplastic 



