TUMOURS ON THE LOWER JAW. 351 



Treatment calls for appropriate nourishment, food must be placed 

 in the mouth, and the stomach tube is sometimes serviceable. The 

 induced or constant electric current should be tried, the poles being 

 applied to the masseter and temporalis muscles ; Frohner states 

 that by its daily use recovery occurs in one to two months. 



(6.) PERIOSTITIS AND EXOSTOSIS ON THE POSTERIOR 

 BORDER OF THE LOWER JAW. 



Circumscribed periostitis sometimes occurs in the horse on the 

 posterior border of the lower jaw at the height of the first molar, 

 and induces exostosis. The most frequent cause is external violence, 

 especially striking against narrow mangers while feeding. The 

 periostitis seldom produces disturbance ; pain is sometimes indicated 

 by careful mastication, but the presence of exostosis usually first 

 attracts notice. On the posterior border of the lower jaw a hard, 

 sharply denned, round, sometimes knobby, painless swelling appears, 

 firmly attached to the bone. Sometimes the swelling is flatter, and 

 may then be mistaken for that produced by alveolar periostitis, in 

 which, however, the rarefaction of bone and the swelling are on the 

 lateral surface of the lower jaw, and mount upwards. Periostitis 

 caused by local injury, on the other hand, remains confined to the 

 posterior edge. 



Prognosis is favourable, the mature exostosis only producing an 

 unimportant blemish. 



Treatment must conform to general principles. Prominent 

 exostoses may be removed : a circular cut is first made through the 

 skin and periosteum, and the chisel or saw then applied. Flat 

 swellings are better left alone. 



(7.) TUMOURS ON THE LOWER JAW. 



True tumours of the lower jaw are much less common in animals 

 than in men. Only enchondromata, carcinomata, and epitheliomata 

 have hitherto been described, and these sparingly. Cadiot and Dollar 

 describe a case of lobulated pavement epithelioma of the lower jaw 

 in a horse, of which an illustration is given overleaf. " The left branch 

 of the lower maxilla opposite the first molars appeared destroyed 

 throughout its entire depth. In two months the tumour destroyed 

 the central portion of the right branch of the lower maxilla, produced 

 great disturbance, general decline, and death." Almost all the 



