4 CLINICAL VETERINARY MEDICINE AND SURGERY. 



Dentigerous cysts in the temporal region usually appear during the 

 first few years of life — in fact, during the period of dentition. At first 

 the dentigerous cyst consists of a soft swelling, flattened or hemi- 

 spherical, painless, or slightly sensitive, varying in size between that 

 of a nut and an egg. Sometimes it persists for long in this condition ; 

 in other cases — and this is the more common — the skin ulcerates 

 towards the centre, or at some point of its surface, the contents of the 

 cyst escape, and a sinus forms. 



As a rule, the opening of the sinus is at the side of the cranium, a 

 little in front of and an inch or so from the base of the ear, — occasion- 

 ally, however, on a level with the scutiform cartilage ; sometimes it is a 



Fig. I. — Pre-auricular fistula due to presence of a dentigerous cyst. 



little further forward, sometimes nearer the middle line or the zygo- 

 matic process ; occasionally it is situated at the base of, or more or 

 less high upon, the free portion of the ear. In Rodet's and several 

 other cases the sinus, though opening some distance up on the 

 conchal cartilage, had originated from near the zygomatic process. 

 The wound is sometimes encircled with a ring of granulation, some- 

 times appears as a simple aperture in the skin, but more frequently is 

 situated at the base of a narrow infundibulum, produced by the retrac- 

 tion of the walls of the fistula. In most cases the parts are swollen, 

 or indurated to a greater or less extent, but when the condition is old- 

 standing,, the swelling or induration which at first existed may almost 

 have disappeared. 



