Etiology. 207 



or frozen feed, or of very cold water may have a similar influ- 

 ence. These influences are particularly potent in cattle when, 

 during winter, they are kept in warm barns and are taken out 

 to drink very cold water. 



Infection undoubtedly often plays an important role. Even 

 in those cases when the disease follows immediately upon a 

 cold, the latter very probably only forms the predisposing 

 cause. Suggestive for an infection as the cause is the fact of 

 the enzootic appearance of the disease in certain localities with 

 a tendency to progress from animal to animal. The bacteria 

 concerned may be those which occur in the buccal cavity and 

 pharynx of otherwise healthy animals (streptococci, bacillus 

 necrophorus, bipolar bacteria) and which may only occasionally 

 exert a morbid effect after the resistance of the mucosa has 

 been lessened by noxious external influences. 



The bacillus necrophorus deserves first consideration as it has 

 repeatedly caused enzootics of angina in hogs (Johne & Meyfarth, Kitt, 

 Schleg) and also appears to have played a role in diphtheritic pharyn- 

 gitis in cattle as observed by Mayr, Strebel, Prietsch. Similar anginas 

 have been observed in sheep (Roche-Lubin, Diem) and in dogs or cats 

 (Robertson, Gray, Symes). 



Young dogs sometimes develop an enzootic pharyngitis during the 

 first weeks, which may pass into pyemia (Friedlierger & Frohner). In 

 a case of croupous pharyngitis of a dog, Ball demonstrated streptococci 

 which he believed to be the cause of the disease. 



Secondary pharyngitis, as a part of the clinical picture of 

 specific infectious diseases, frequently appears either sporadical- 

 ly or enzootieally. Such diseases are strangles, influenza of the 

 horse, buffalo plague, hemorrhagic septicemia of cattle and of 

 swine, fowl cholera, anthrax, diphtheria, purpura hemorrhagica, 

 variola, etc. Pharyngitis due to the bacillus suisepticus (septi- 

 cemic angina) occasionally appears in enzootic form (Graffun- 

 der & Schreiber, Pr. Vb.)". 



Inflammatory processes of neighboring tissues such as the 

 nasal and buccal cavities, the larynx, the air sac, the esophagus, 

 and of the bones of the face not infrequently extend to the 

 mucosa of the pharynx. 



Chronic pharyngitis is quite common. It is, however, of 

 no great importance from a clinical standpoint, since it does 

 not lead to important pathologic disturbances. It generally 

 develops after an acute phar^aigitis or after repeated, long-con- 

 tinued irritation. 



Susceptibility. Horses and swine are most prone to de- 

 velop disease of the pharynx. The marked difference in the 

 predisposition of various groups of animals partially depends, 

 perhaps, upon the fact that the tonsils of horses and swine pos- 

 sess several foramina coeca, those of other animals only single 

 ones. Hence, it appears that the tonsils of horses and swine 



