xiii, b, 5 Haughwout: Flagellated and Ciliated Protozoa 247 



not only in the tissue, but in the blood vessels as well; in fact, 

 the microscopic picture was similar to that seen in the case of 

 human balantidiosis. 



Walker also points out the fact I have mentioned that an 

 individual may harbor Balantidium over long periods of time, 

 apparently without sustaining harm. But sooner or later, he 

 adds, the patient so parasitized develops balantidial dysentery. 

 The periodic appearance of the parasites in the stools that he 

 notes is a phenomenon seen frequently in connection with the 

 intestinal Protozoa as a group. 



The oral apparatus of Balantidium is similar to that of a 

 number of free-living Heterotrichida, and indeed Balantidium 

 is suspected of being capable of existence free in pond water. 

 The oral apparatus of this organism does not seem, at first 

 glance, particularly to adapt it for penetration of the tissues; 

 and if we are to adopt the views of Walker and of Manlove, 

 it remains to discover how this may be brought about. 



Bowman quotes Glaessner(i9) as having recovered a very 

 active diastase and a fairly strong hsemolytic substance in ex- 

 tracts of Balantidium coli from the fasces. These ferments 

 exerted no effect on dilute albumen, on peptone solution, or on 

 fibrin. One naturally asks why they should and why they should 

 be concerned in cytolysis. Any such supposition seems to me 

 to be entirely untenable. It seems to be much more probable 

 that Glaessner, after all, merely isolated some of the normal 

 digestive ferments of the parasite. Both diastatic and hsemolytic 

 ferments seem to be exceedingly necessary to the carrying out 

 of the normal anabolic processes in an animal living in such an 

 environment as that in which Balantidium lives. A diastatic 

 ferment ("amcebodiastase") has been isolated from amoebae. 

 Proteolytic ferments have been isolated from other protozoa, and 

 their action has been the subject of considerable study by 

 Nirenstein, Greenwood, Metchnikoff, and others. 



It is still an open question whether Entamoeba and Balanti- 

 dium enter the tissues through or between the cells and whether 

 the entrance is effected mechanically or by the aid of cytolysins. 

 Manlove (28) quotes Crowell 1X as stating his belief that the 

 question of the essential pathogenicity of Balantidium is not 

 yet absolutely settled. As to the invasive power of the or- 

 ganisms, Manlove says : 



Doctor Crowell expressed the theory that it seems reasonable to conclude 

 that some substance (toxin?) originating from the balantidia is able to 



11 Crowell, B. C, personal communication. 



