126 THE SURGICAL ANATOMY OF THE HORSE 



which, it will be readily understood, renders their excision much 

 more troublesome, owing to the profuse haemorrhage which will 

 inevitably occur. 



In removing such growths, the ear is first plugged with cotton 

 wool to absorb blood, etc., and prevent its inward passage. An 

 incision is then made through the skin on both sides of the concha 

 around the base of the growth. The skin is next pressed slightly 

 away from the tumour and the cartilage is incised, the incision 

 passing through the zone of healthy cartilage surrounding the tumour. 

 (This will admit of the flaps of skin being brought into apposition 

 more readily when the edges are sutured to enclose the cartilage.) 

 The largest vessels are ligatured, and it may be necessary to apply 

 the actual cautery to arrest the hemorrhage from the smaller ones, 

 when the flaps of skin may be sutured as directed. The plug of 

 wool is now removed, and a clean one inserted, completely filling up 

 the interior of the concha. Dry dressing should then be dusted 

 over the part, or the wound may be covered with iodoform and 

 collodion. 



Dentigerous Cysts. — Occasionally there is found on the anterior 

 aspect of the base of the ear an opening from which a serous 

 discharge is ejected if the surrounding parts be compressed. This is 

 the external opening of a sinus, which, if probed, will usually be found to 

 take a direction downwards, extending to the zygomatic process of 

 the squamous temporal bone and sometimes even to the malar. In 

 the latter cases the sinus is from two to three inches in length. 

 Further exploration will reveal the presence at the bottom of the 

 sinus of a hard body, and this body will be subsequently found to 

 be of the nature of a tooth. In this situation it acts as a foreign 

 body to the surrounding structures, and leads to the development of 

 a sinus. 



As in the case of the presence of other foreign bodies, formation 

 of a considerable amount of fibrous tissue may result, and an abscess 



