146 



General Biology 



in form due to ameboid motion, as for example, when they penetrate the 

 epithelial lining of the intestinal glands. 



This parasite is a common inhabitant of the intestine of the 

 hog but it causes no lesion there. On rare occasions it is apparently 

 transferred to man where it gives rise to more or less extensive ulcera- 

 tions in the large intestine (rarely in the lower end of the small intestine) 

 accompanied by persistent diarrhea. The disease may terminate fatally. 



These parasites are also 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. Often they are found in 

 lymph-vessels and veins, but they do not seem to be distributed by the 

 streams of these vessels. They have likewise been found in the liver. 



They do not seem to produce a toxin but do a mechanical injury 

 only, although this injury opens paths through which bacteria often 

 cause infections. 



The ulcers caused by this organism resemble those caused by 

 entamoeba histolytica. 



Fig. 60. 



A. Partially schematic drawing of Trichomonas intestinalis. 



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 Benson and 

 Grassi and Schewiakoff; D, after Wenyon.) 



