No. 604] THE CASE OF TRICHOMONAS 219 



played by the goblet or chalice cells of the crypts of 

 Lieberkuhn in this respect. Trichomonas, after congre- 

 gating in vast numbers in the fundi of the crypts, with a 

 consequent bulging of their walls forces its way into the 

 goblet cells. It is not deterred by the nucleus or the cell 

 wall at the basement end, but throws the former out of 

 place and breaks through the latter to assume a position 

 beneath the epithelium of the crypt. The wall having 

 been ruptured and an avenue created to the deeper tissues, 

 other flagellates follow by the same path until many are 

 present between the epithelium and the basement mem- 

 brane. But Trichomonas does not halt here. It is now 

 filled with the spirit of the invasion and quickly pushes 

 through the basement membrane into the loose connective 

 tissue of the mucosa. This tissue is speedily overrun by 

 the advancing hosts, the barrier of the muscularis mu- 

 cosae is passed and the entire submucosa exposed to the 

 ravages of the parasite. 



It is here that we recognize Trichomonas in a new role. 

 Having experienced its first taste of blood its whole nature 

 is changed; it becomes another animal, raging through 

 the tissues and impeded by no protective action that the 

 host organism is able to muster to the defense. Here then 

 we must recognize Trichomonas as a cell parasite, an or- 

 ganism that has the power to actively invade living cells 

 and to bring about their destruction. One may remark 

 that the type of cell invaded is highly specialized type, 

 and one that, by its nature, is more or less open to in- 

 vasion. But the fact remains that host cells are invaded, 

 and actively invaded; and in this circumstance we can 

 detect, in the behavior of Trichomonas, a foreshadowing 

 of those cell-invading activities regarded as character- 

 istic of the sporozoa. 



But of course the host-organism must put up some de- 

 fense, and sometimes a very vigorous defense is offered, 

 chiefly by means of its batteries of endothelial and other 

 phagocytic colls. These come out in numbers to meet the 

 invaders and as a result many of the flagellates are en- 

 gninMl. citlioi- by sindo ondotliolinl cells or in giant cells. 



