120 r>. H. WENRICH 



by Kofoid and Swezy ('15) and two by Kuczynski ('14, '18). 

 The structure and division of Trichomonas muris were described 

 in these papers as well as in the earher one of Wenyon ('07). 

 Since I have been able to secure some material which seems to 

 be especially favorable for the study of cell structure and division 

 in this species, and since my findings are not in entire agree- 

 ment with any of the authors mentioned above, it would seem 

 to be worth while to place on record my observations. I have 

 begun an investigation of the various intestinal protozoa of 

 rats and mice, but the present account will be limited to the one 

 species. 



MATERIALS AND METHODS 

 A. Materials 



Trichomonas muris (Hartmann) is found chiefly in the coecum 

 of mice and to a less extent in the large intestine. Only rarely 

 has it been found in the small intestine and then only at the 

 lower end. 



The first material from the coecum of a mouse (Mus musculus) 

 in which I found the division stages numerous was secured in 

 December, 1916. Slides made from this material have proved 

 to be the most valuable in the collection, and many of my figures 

 have been made from them. Since that time 102 additional mice 

 have been examined, of which fifty-one were wild and fifty-one 

 were albinos. Of the wild mice, nine were Peromyscus leucopus 

 and the others were the house mouse, Mus musculus. Only 

 two of the Peromyscus and only five of the forty-two house 

 mice showed infection with Trichomonas muris, while fifteen 

 of the fifty-one white mice were found to harbor this species. 

 Young mice showed less tendency to infection than adults and 

 the degree of infection was extremely variable. It ranged from 

 occasional specimens to cases when the entire contents of the 

 coecum appeared to consist of Trichomonas and a few bacteria. 

 In these latter cases division stages were common in the mass 

 of coecal contents as well as near the mucous membrane. 



