No. 604] THE CASE OF TRICHOMONAS 



223 



cult to say. That its absence would determine a more 

 homogeneous cytoplasm at all stages of growth is, of 

 course, obvious, but its effect upon the cell structures 

 such as chromatic line, blocks and axostyle, and upon the 

 relative size and distribution of the daughter nuclei is still 

 not clear. It can scarcely be wondered at, however, that 

 such a radical change in the manner of nutrition of a 

 parasite would be accompanied by alterations of some de- 

 velopmental significance. 



Upon superficial observation it appears that, in a para- 

 sitism of this sort, when the organisms are driving ever 

 deeper into the tissues, one of the essential features of 

 complete parasitic activity is absent, namely, the ability 

 to escape from the tissues and to secure a position by 

 virtue of which the parasite can insure the possibility of 

 reaching other hosts. Without this possibility provided 

 for, no parasitism can be called complete. Although, in 

 the case before us, many of tlie parasites are so buried in 

 the tissues, a study of the trend of the infective process 

 as a whole has revealed a m-aiis bv which the organisms 

 return to the cecal content after tlieir invasive career has 

 ended. This is by spreading downward and inward 

 through the reticular tissue of the cores of the villi and 

 pushing the epithelium off of the villus tips. Behind the 

 epithelial wall at these points the parasites congregate 

 in vast numbers until finally the epithelium breaks and 

 liberates the flagellates into the cecal contents. That this 

 process of escape from the tissues takes place only over 

 certain areas of the intestinal wall is apparent; but the 

 fact that it occurs at all is suflicient evidence to indicate 

 that Trichoiiioiias is not wliolly lacking in this essential 

 element of successful parasitism. 



And finally we find in the case of Trichomonas one 

 more lesson, and this is one for the etiologist, this being 

 of course any one who concerns himself seriously with 

 disease etiology. This important iXM'son, confroiiliMl with 

 a disease of unknown cause, busily sct^ al'oui t.^ discover 

 the germ; and having found the uvrin, ho a- bu>ily en- 

 gages himself in ascertaining means and Tueasures 



