496 



PROTOZOA 



A number of cercomonada, none of them well studied, have been 

 observed in different animals, as well as in man. 



Cercomonas hominis (Davaine, 1854) was observed in the dejec- 

 tions of a cholera patient by Davaine. The body is 10/^ to 12/J. long 

 and pear-shaped, pointed posteriorly. The flagellum is twice as long 

 as the body. The nucleus is difficult to see. Davaine also reported 

 a smaller form in the stools of a typhoid patient. Other observers have 

 noticed similar forms in human stools, some associated with amoeba 

 coli. Similar forms have been seen also in an echinococcus cyst of the 

 liver, in the sputum from a case of lung gangrene, in the exudate of a 

 hydropneumothorax, and a few times in the urine (bodo urinarius). 

 They are all probably harmless comensals. 



Polymastigina. 



The order polymastigina consists of flagellates having several flagella 

 projecting from different parts of the body. The majority of the forms 

 known are parasitic in certain fish. 



Donne* in 1837 described a form belonging to this group which he 

 found in the human vagina, and which he therefore called trichomonas 

 vaginalis. It has been found by other observers to be a frequent habitant 



FIG. 150 



FIG. 151 



Trichomonas vaginalis. (Blochmann.) 



Lamblia intestinalis. (Schewiakoff.) 



of the vagina at all ages. It has also been found a few times in the acid 

 urine of males. The mode of infection of the female is unknown. The 

 body of the parasite at rest is pear-shaped, but during action its amreboid 

 movements cause it to assume various shapes. The size varies from 12// 

 to 25// long and 8// to 15/* wide. The protoplasm is finely granular, 

 excepting for two rows of larger granules which begin on either side of 

 the nucleus and converge posteriorly. From the anterior part project 

 three to four flagella, which seem to begin at a basal thickening near to or 

 connected with the more or less oval, indistinctly vesicular nucleus. From 

 the origin of the flagella an undulating membrane extends backward. 

 The body also seems to possess a certain linear structure connected with 

 the membrane. Contractile vacuoles have not been seen. 



