290 



VETERINARY PATHOLOGY. 



them (Williams). Facial bulging is a common symptom of 

 them and there may be an excessive mucus discharge from the 

 nostrils. Cystic odontomata maj- produce super-resonance, which 

 is useful in differentiating them from empyema of the facial 

 sinuses. 



These tumors are derived from the enamel organ, dentine 

 papilla, or the tooth follicle. Their derivation to some extent 

 determines their structure. Those derived from the enamel 

 organ are composed of an enamel covering and in some cases 

 the entire odontoma is enamel. Dentine is usually the pre- 

 dominating tissue in those derived from the dentine papilla. 

 From the tooth follicle there are usually formed cystic odonto- 

 mata, although thejr ma_v be fibrous or may contain ossified cen- 

 tres and cementum. Their structure varies considerably and it is 

 not rare that all of the above structures are represented in one 

 odontoma. 



In size, odontomata ^•arv from microscopic masses to irregu- 



Fig. 147. — Photograph of an Odontoma of tht- intpiior maxilla of a horse. 



