xiii, b, 5 Haughwout: Flagellated and Ciliated Protozoa 251 



penetration of the cell by the parasite, but N oiler, (39) who did, 

 states that he saw — 



a trypanosome of which the pointed hinder end had already penetrated into 

 an epithelial cell. The flagellum-bearing anterior end beat violently and 

 incessantly, whereby the trypanosome penetrated further and further into 

 the cell. After I had watched this spectacle for about five minutes the try- 

 panosome, which had so far penetrated into the cell as far as the middle 

 of its body, suddenly shot into the cell and stirred up the granular cell- 

 contents by its lively movements. Since, however, the cell was torn on its 

 opposite side the trypanosome shot out of the cell again. 



In discussing the type of cell attacked by the trypanosomes, 

 Minchin and Thomson are somewhat in agreement with the 

 observations of Walker. They never saw intracellular stages of 

 the trypanosomes in the cells of the epithelial crypts. The 

 trypanosomes never occurred in any cell that was not definitely 

 a part of the general epithelium, and the appearances they saw 

 seemed to suggest that "the attack is usually made on the side 

 of the cell; the occasional, though rare occurrence, however, of 

 intracellular stages in quite young cells, shows that the trypa- 

 nosomes can penetrate into epithelial cells before the separation 

 between them has developed." 



Of course, the general character of the epithelium of the ali- 

 mentary tract of the flea probably differs in important details 

 from that of the epithelium in the human digestive tract, but 

 the conditions that exist in certain cells and that may profoundly 

 influence tissue invasion are suggested in the following paragraph 

 from the paper of Minchin and Thomson : 



The trypanosomes attack by preference the fully-formed, but still young 

 and vigorous cells, which may contain granules of the normal type and 

 even yellow bodies, but no fatty deposits; cells which may be well char- 

 acterized as adolescent in type, and which, stain a clear, light-grey with 

 iron-haematoxylin after Flemming-fixation. It is in such cells that the 

 earlier stages of the intracellular multiplication are to be found in flourish- 

 ing condition and often in considerable numbers; but if the trypanosomes 

 are numerous the cell soon becomes exhausted. 



Evidence of the possibility of the transmission in man of 

 Trypanosoma gambiense by coitus was brought forward by Koch, 

 (25) in 1907, and the transmission of Trypanosoma equiperdum 

 in dourine has long been an established fact, although trypa- 

 nosomes have not been demonstrated in the seminal fluid, and the 

 possibility of even slight abrasions of the mucous membranes of 

 the contracting parties still remains. 



Hindle(22) has made a study to determine the possibility of the 

 entrance of trypanosomes through the intact skin and mucous 



