2o6 RESEARCH IN PROTOZOOLOGY 



The main factors concerned in the diagnosis of uncompHcated 

 amoebic dysentery are now generally understood. The old chronic 

 cases, however, occasionally present features that make it a mat- 

 ter of difficulty to distinguish between an old amoebic process 

 with a heavy secondary bacterial infection of amoebic ulcers, and 

 a late stage of bacillary dysentery. As a matter of fact, both are 

 secondary manifestations of a similar nature and for purposes 

 of treatment the uncertainty is not of great moment. It must be 

 remembered that unchecked amoebic processes may lead to marked 

 anatomical changes involving the entire structure of the bowel 

 wall. With the secondary bacterial invasion that always accom- 

 panies this, come cellular manifestations, sometimes slight — some- 

 times marked. In the marked instances there are extensive necrotic 

 cellular changes (karyorrhexis, karyolysis, etc.), and one even may 

 find an occasional macrophage. Better criteria are needed for the 

 interpretation of these pictures. 



Furthermore, an effort should be made finally to define the 

 significance of Charcot-Leyden crystals. Acton (1918) has dis- 

 cussed them and his conclusions, in which I concur, were con- 

 servative. More recently, Thomson and Robertson (1921a and b) 

 have taken the extreme view that their presence is pathognomonic 

 of Enfamo'ba Jiisfolyfica infection. To my mind, the question is 

 still open. The remarks of Connal (1922) concerning the finding 

 of these crystals in a case of infection with Isospora houiUiis are 

 of interest. As a matter of fact, the appearance of Charcot-Leyden 

 crystals in the feces is quite as irregular as that of cysts of 

 E. histolytica and they lack the positive value that attaches to find- 

 ing the latter. 



Balantidial dysentery is of comparatively rare occurrence. Ac- 

 cordingly, the studies of the bowel exudate in that condition that 

 have been published by me (1920 and 1924a and b) are based on 

 very few cases. For that reason, no opportunity should be lost, 

 by the careful study of other cases, to check my findings. The 

 situation is complicated by the designation of two species of Balan- 

 tidium in the pig by McDonald (1922). It should be ascertained 

 if both Balantidiuin suis and B. coli will parasitize man and, if 

 so, if both are capable of j^roducing dysentery. Settlement of these 

 questions may explain numerous conflicting views as to the patho- 

 genicity of B'llantidium to man. The reader is referred to the 

 papers of Strong (1904), Walker (1913^'), and Manlove (1917). 



