No. 604] THE CASE OF TRICHOMONAS 



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trophozoites measuring from 4 to 5 /* in length and about 

 3/M in breadth, equipped with anterior flagella at least, 

 and possessing a relatively large nucleus and minute 

 blepharoplast. The other organelles characteristic of the 

 mature trophozoites appear to develop by degrees as the 

 trophozoite increases in size. 



These, then, are the two chief methods of reproduction. 

 Ordinarily the course is very simple, but from a study of 

 both fresh and stained material it is clear that several 

 complicating factors may enter. For instance there is 

 evidence that conjugation may occur, not only between 

 two individuals but perhaps between three or four. This 

 process is aided by the extrusion of a viscid membrane 

 by those organisms that have rounded-off. This naturally 

 helps to cause the individuals to adhere together. After 

 conjugation this viscid membrane appears to harden into 

 a protective cyst wall. Usually the size of the single cyst 

 is about 10 to 12 /t, but in the ''fused" or conjugated 

 forms the diameter may reach 20 to 30 /a as seen in fresh 

 preparations. It is also clear that the "double" and 

 "triple" cysts sometimes seen may represent a division 

 of the original cyst, whereupon each daughter cyst con- 

 tinues independently the production of daughter cells by 

 the usual method, described above. 



Keproducing by the methods described above. Tricho- 

 monas ordinarily lives in the intestinal tract and causes 

 no recognizable injury to the host. It has never been re- 

 garded as other than a harmless commensal. Eecent 

 studies^ have demonstrated, however, that, upon occasion, 

 this flagellate may depart from its usual mode of life, may 

 penetrate the tissues of its host and cause fatal lesions, 

 not only in the walls of the intestinal tract, but in the liver 

 as well. It is especially this assumption of a pathogenic 

 role, this sudden adaptation to a new manner of life, to- 

 gether with the morphological changes that accompany it, 

 that constitute perhaps the most interesting phase of the 

 life of Trichomonas. First, how does it liappen that the 

 flagellate gets started on its tissue-desi-toiling career? 



