DISEASES OF THE HEAD. 245 



DISEASES OF THE HEAD. 



I.— DISEASES OF THE LIPS AND CHEEKS. 



(1.) WOUNDS AND BRUISES. 



In horses, wounds of the lips frequently result from bites or kicks, 

 from collisions and falls on hard ground, or from entanglement with 

 sharp portions of the harness, or with nails, hooks, etc., fixed in 

 stable racks and mangers. Bruises are produced in a similar manner, 

 and by the severe and repeated application of the twitch. The 

 corners of the mouth may be injured by thin or badly-fitting bits, 

 especially in young and hard-mouthed horses, or in those suffering 

 from brain disease, whilst the cheeks are sometimes lacerated by 

 kicks, horn thrusts, and, on their inner surfaces, by the sharp edges 

 of the molars. Cattle at grass may suffer from torn wounds produced 

 by dogs, while sporting dogs may be bitten by the quarry. 



The great mobility of the injured parts, and the constant soiling 

 which occurs during mastication, almost always interfere with th) 

 healing of bruises and contused wounds. On the other hand, 

 reparative processes are assisted by the richness of this region in 

 blood-vessels and loose connective tissue, so that healing sometimes 

 takes place by primary intention, even when wounds are extensively 

 bruised, their edges already dry, and their flaps dissected from under- 

 lying tissues over considerable areas. Deep wounds in the corner 

 of the mouth, where the mucous membrane is divided and the 

 opening of the mouth lengthened, give most trouble. Perforating 

 wounds of the cheek also heal with difficulty, and sometimes produce 

 fistula?. Injuries to the great venous plexus in the cheek occasion 

 considerable bleeding, which, however, is seldom dangerous. The 

 division of Stenson's duct often results in salivary fistula. Emphy- 

 sema of the facial region frequently accompanies wounds of the 

 cheek, but calls for no special treatment, and usually disappears 

 spontaneously. Necrosis of the margins of wounds may produce 

 defects in the lips and cheeks, which both injure the animal's 

 appearance and interfere with feeding and drinking. Such defects 

 frequently follow wounds in the corner of the mouth, where the 

 buccal opening becomes lengthened (Makrostomy). 



