420 



Tumors. 



cular tumor and the deformed tooth, and giving- rise to the type 

 known as osteocystoma capsiilare dcntifernm. Occasionally in 

 young horses at the base of the ear over the temporal bone cysts 

 may be found which contain one or several imperfect teeth, 

 usually opening by a fistulous sinus upon the skin ; these are 

 blind tubular invaginations from the skin, lined with mucous 

 membrane and provided with a bony covering or with small 

 bone platelets in simulation of the alveolar process of the jaw; 

 they originate from the branchial arches and are known as 



Fig. 129^ 

 Odontocyst of lower jaw of cow. 



Fig. 130. 

 Osteocystoma dentiferum of liorse. 



branchiogenoiis dental foUicidar cysts {odonto-temtoma bran- 

 chiale, odontocystis braiichiogcnetica).'^ This type of cysts is 

 only rarely met in other animals; Siedamgrotzky encountered 

 two dental cysts in the ethmoidal turbinate in a hog; Verwey has 

 recorded one in the petrous portion of the temporal bone in 

 a dog; Hertwig met a dental cyst in an ox. 



Teeth are sometimes found in dermoid cysts and teratomata 

 in other parts of the body, especially in this type of growth in 



* For fuller description v. Kitt, Lehrbuch der pathol, AnatonUe der Haustieve, 

 Stuttgart, F. Euke's Verl. II Aufl., 1901. 



