248 The Philippine Journal of Science ms 



produce necrosis of the tissues, and the inflammatory phenomena that occur 

 later are the result of the action of the accompanying bacteria. Also one 

 could imagine that this hypothetical toxic substance from the balantidia 

 produces a cytolysis of the epithelial cells of the mucosa with which they 

 come in contact and so forms a portal of entrance to the deeper tissues for 

 the organisms. 



Eestating this view to me, Crowell V2 holds that it is logical 

 to suppose that, if the balantidia are capable of producing within 

 the tissues a substance that brings about necrosis, this same 

 substance might be employed in the initial penetration of the 

 intact epithelium. 



However, it may be pointed out that a fundamental objection 

 that might be opposed to this hypothesis is the fact that sub- 

 stances that are capable of producing marked injury to the 

 unprotected connective and other tissue elements of the sub- 

 mucosa may have no effect whatever on the healthy epithelium, 

 the chief function of which is constantly to protect the under- 

 lying tissues from substances that would be injurious. To in- 

 jure by a toxic substance the intact epithelium would, it seems 

 to me, require a stronger toxin than the changes produced, once 

 having effected penetration, would indicate. That is, of course, 

 provided there is no specific epitheliolysin, of which there is 

 no evidence. On the other hand, much of the evidence I have 

 already quoted points to the mechanical invasion of the intestine, 

 rather than to the employment of cytolysins. Walker has stated 

 his belief that entrance is accomplished by the pushing aside 

 or rupture of the epithelium, and similar evidence in the case 

 of Trypanosoma leivisi seems to have been produced by Minchin 

 and Thomson (36) and by Noller, (39) in the case of Trichomonas 

 by Hadley, and in the case of Trypanosoma gambiense by 

 Hindle.(22) 



Carrying the case to the parasitic Rhizopoda, the active, 

 powerful pseudopodia, formed mainly of ectoplasm as seen in 

 Entamoeba histolytica, are in marked contrast to the relatively 

 blunt, inactive pseudopodia of Entamoeba coli, which contain 

 comparatively little ectoplasm, and suggests the possibility that 

 it is this difference in the structure of the pseudopodia that 

 enables Entamoeba histolytica to push its way between the cells. 

 Are cytolytic agents necessary here? Or, in the case of Ba- 

 lantidium, are the cell membranes or bridges between the cells 

 able to withstand the powerful currents set up by the cilia 



12 Crowell, B. C, personal communication. 



