FISTULA OF THE EAR. 
113 
too short, causing the head piece to press on the base of the eai. lhe 
following case of Holier’s belongs to the same category. 
A horse showed powerful cramp-like movements immediately a finger was 
introduced into one or other ear. Passing it into the left eai, the horse at 
once endeavoured to bring the left hind-foot as near the ear as possible, and 
rapid movements were made with the muscles of the hind-foot and of the 
neck. Pressure on the base of the ear immediately produced these cramp* 
like movements. The same happened on the right side. Pressure of the bit 
caused similar symptoms, so that the animal was useless for work. Exami¬ 
nation of the ears and auditory opening during life showed no change ; 
hearing was undisturbed. Unfortunately Moller was unable to make a. post¬ 
mortem, but during life he was unable to detect the slightest change m the 
ears. 
(5.) FISTULA OF THE EAR. DENTIGEROUS CYSTS. 1 
Fistulee are sometimes seen in the horse at the base and near the 
anterior surface of the cartilage, extending downwards towards the 
malar bone for a distance of 1 to inches. A little serous fluid 
discharges on pressure. On introducing a probe, a hard body may be 
discovered at the bottom of the canal which, if the latter be laid open, 
will be recognised as of the nature of a tooth. Sometimes several small 
teeth are found in the swelling. Strictly speaking, the condition is not 
a fistula, but represents the remainder of the incompletely developed 
branchial arch. On this account the fistula sometimes communicates 
with the guttural pouch. 
The phenomenon must be referred to the development of embryonic 
branchial arches and clefts. Sometimes the lateral plates of these visceral 
cavities are ruptured, and remain so, thus giving rise to fissures m the ear 
pharynx oesophagus, and neck (fistula auris et colli congenita), whilst paitia 
persistence of the unruptured embryonic furrows produces blind sacs and 
dermoid cysts. The dental furrow which occurs in this portion of the 
embryonic apparatus results from a primitive fold of the buccal epithelium, 
which as in the jaw, can produce enamel. The teeth are oftenest found m 
the squamous portion of the malar bone. Several —ix from 2 to 4—may be 
present; they resemble molars. Sometimes a cyst alone is present, and the 
tooth wanting. 
Such teeth may be present (abnormally) in other positions, as the 
gums, the superior maxillary sinus, the testicle, and the ovary. In the 
malar bone they often remain long unremarked, until either acute inflam* 
mation produces swelling and prominence, or until attention is accidentally 
directed to the fistulous opening. They are commonest in young animals, 
especially during the period of dentition, and may even be seen within a 
few weeks of birth. The swelling is hard, and firmly connected with the 
i See also Cadiot and Dollar’s “ 
also p. 298. 
y.s. 
Clinical Veterinary Medicine and Surgery,” pp. 1 et seq. and 
I 
