THE PROTOZOA 



145 



exhibit changes in form due to ameboid motion, as in penetrating the 

 epithelial lining of the intestinal glands. 



"The organism is a common inhabitant of the intestine of the 

 hog where it causes no lesion. On rare occasions it is apparently trans- 

 ferred to man and gives rise to more or less extensive ulcerations in 

 the large intestine (rarely in the lower end of the small intestine) ac- 

 companied by persistent diarrhea which may terminate fatally." 



They are found in the lumen and walls of the intestine but 

 usually they penetrate the epithelial wall and lie next to a gland. Some 

 collect in the lymph-nodules while often they are found in lymph-ves- 

 sels and veins, but they do not seem to be distributed by streams of 

 these vessels. They have been found in the liver. 



They do not seem to produce a toxin but do a mechanical i^i- 

 jury only, although this injury opens paths through which bacteria often 

 cause infections. 



Fig. 



A. Partially schematic drawing of Trichomonas iwtestinalis. 



B. Trichomonas muris dividing (5 stages). 



C. Lamblia intestinalis. a, flagellated form ; b, cyst ; c, flagellated form viewed 

 from the side. 



D. Cercomonas hominis. a and b, show different forms of the organism ; 

 c, cyst. 



(From Kolle-Wassermann ; B, after von Kuczynski ; C, after Betison and 

 Grassi and Schewiakoff ; D, after Wenyon.) 



