264 BALANTID1UM COLl. 



stomach that the Balantidia must reach their destined habitation, for 

 an entrance per anum is by the nature of the case impossible. 



Man becomes infected with Balantidium by eating substances with 

 which the encapsuled animals have come into contact ; how this con- 

 tact occurs we can hardly tell, it is simply the result of the same 

 countless chances which determine the ubiquitous distribution of eggs 

 of Helminths. Then, of course, the Balantidivm-cysts are not 

 imprisoned within the pig's dung, but if this be broken and dried up, 

 they may be spread about without loss of the power of development, 

 and may be conveyed to man with an ease proportionate to the 

 closeness of the local relations obtaining between him and the swine. 



As to the pathological import of Balantidium, we might answer 

 much in the same words as in regard to the related Infusoria, the in- 

 testinal Monads, and the Amaebce. It is uncertain whether they 

 can be regarded as having actually a power of originating disease. 

 Although they seem to be constant in pigs, no pathological pheno- 

 mena result. Of course this is not decisive, for we know hrw differ- 

 ent organisms are very variously affected by different influences ; and 

 it is perhaps worth noting, in connection with the above facts, that 

 the excrement of pigs has usually a loose and stinking character, 

 which is not normally the case in man. 



But granted that we cannot directly affirm that the parasitism of 

 Balantidium determines of itself a pathological state, it does not in 

 the least follow that its presence is indifferent to its host. Bather it 

 is, d priori, very probable that the movements of the animals, present 

 as they are in thousands and hundreds of thousands, occasion a state 

 of irritation which might easily increase and aggravate an existing 

 disease. For this reason it is advisable, when the occurrence of this 

 parasite has been proved, to take measures against it, as well as 

 against any other disease. 1 



It is doubtful whether these parasites can live in a perfectly 

 healthy intestine. Hitherto they have been found only in stools of 

 patients otherwise diseased. If these changes be not regarded as 

 a consequence of the parasitism, then evidently one must conclude 

 that an abundant secretion of mucus (for the stools of infested persons 

 are usually pulpy and diarrhcetic) is a condition favourable to the 

 existence and reproduction of Balantidium, as, indeed, we have 

 formerly concluded of the other intestinal Infusoria. But, on the 

 other hand, it is doubtful whether we are warranted in ranking Bal- 

 antidium among the so-called " putrefactive Infusoria," since they live 

 more upon the fluid chyle than upon the secretions of the intestine. 



1 As to the means to be used (clysters of acetic and tannic acids), see especially the 

 reports of Henschel's experiments (loc. cit.). 



