PROTOZOA 197 



face and some in the deeper strata, with low power, appearing 

 brown, surrounded by a transparent areola. 



Stab-culture. Very profuse along the needle-track, in the 

 form of a cone after two days, the colonies having gathered 

 at the apex. 



Potato. A dirty gray, not very abundant, layer, somewhat 

 viscid. 



Staining. With ordinary methods: also Gram's method. 



Pathogenesis. If a pure culture is injected into the mam- 

 mary gland of sheep, a "mal de pis" is produced which 

 causes the death of the animal in twenty-four to forty-eight 

 hours. The breast is found edematous, likewise the thighs 

 and perineum; the mammae very much enlarged, and at the 

 nipples a blue- violet coloration. The spleen is small and 

 black; other animals are less susceptible. In rabbits abscesses 

 at the point of infection, but no general affection. 



CHAPTER XXVII 

 PROTOZOA 



PROTOZOA are unicellular animal organisms, minute as bac- 

 teria, and differing from bacteria in the methods of repro- 

 duction. Their structure and functions are more complex, 

 although the borderland is ill denned. A nucleus is usually 

 present. 



Divisions. There are four grand divisions of protozoa: 

 (i) Sarcodina, containing 5500 species; (2) mastigophora, 

 containing 500 species; (3) infusoria, containing 700 species; 

 (4) sporozoa, containing 300 species. 



Sarcodina are chiefly marine forms, with processes change- 

 able in shape. Examples: Ameba, foramnifera, entameba, 

 parasitic for man. 



Mastigophora have undulating flagella and are known 

 as flagellates; to this division the trypanosomata belong. 

 Example: Trypanosoma. 



