CHAPTER X. 



DISEASES CAUSED BY PROTOZOA 

 GENUS AMEBA. 



§ 295. General discussion of Ameba. The ameba 

 belong to the class Sarcodina. They include the simpler 

 forms of the protozoa. The genus ameba is provided with 

 lobar or pointed pseudopodia. A few of these have become 

 parasitic. So far as seems to be known, these parasites, with 

 possibly a few exceptions, do not produce noxious products 

 like bacterial toxines or ptomaines, but whatever damage they 

 may cause is due to the mechanical disturbances set up by 

 their presence and multiplication. The genus ameba has 

 very few pathogenic species. The best known of them is 

 Ameba coli, the supposed cause of a form of dysentery in man. 

 In animals but few species have been found to stand in a 

 causal relation to a morbid process. The term ''amebiasis'' 

 has been introduced by Musgrave and Clegg to denote an in- 

 fection with ameba. 



INFECTIOUvS ENTERO-HEPATITIS IN TURKEYS. 



Synonym. Blackhead. 



^ 296. Characterization. This disease of turkeys is 

 characterized by thickening of areas or of the entire walls of 

 the ceca and areas of tissue degeneration and necrosis in the 

 liver. 



J^ 297. History. In the fall of 1893, Prof. Samuel 

 Cushman of the Rhode I.sland State Experiment Station sent 

 a few specimens of the affected organs of turkeys which had 

 died of "blackhead" to the Bureau of Animal Industry, where 



