TUMORS. 335 



projection. The teeth vary from an irregular conglomerated mass 

 of dental tissue to those perfect in form and structure. The c(jn- 

 stant production and accumulation of the containing viscid fluid 

 results in enlargement of the cyst and frequently rupture of the 

 capsule and the production of a fistula. The most freciuent lo- 

 cation of dentigerous cysts is near the base of the ear in the 

 region of the parotid gland although they may occur in any 

 other place especiallj' in the ovary and testicle. They are most 

 common in horses. 



Cholesteatoma is a teratoma composed of pearl like masses 

 of epithelium in which there is more or less cholesterin. They 

 are not common but have been observed in the brain, (choroid 

 plexus and tuber cinereum) and urinary organs. There 

 was recently obtained from near the kidney of an ox, a mass of 

 substance of a waxv consistency, that gave the t}'pical reaction of 

 cholesterin and was probablv a cholesteatoma. 



CYSTS. 



DEFINITfON. 

 ETIOLOGY. 



Retained seerefioii. 



Obstructed outflow. 



Excessive production in ductless glands. 



Retention of hemorrhagic e.rtravasate. 



Colliquation necrosis. 



False bursae. 



Parasites. 

 STRUCTURE. 

 VARIETIES. 



Retention; Atheroma. 



E.vudation; Hygroma, Shoe boil, Capped hock. Meningocele. 



Extravasation; Hematocele, Hematoma. 



Degeneration; Colliquation necrosis. Hydalifonn 



Pu'^^-asitic; E chinoccosis, Mcasley pork. 



Dermoid: Cutaneous. Dentigerous 

 SECONDARY CHANGES. 

 EFFECTS. 



A cyst is a bladder like growth surrounded by a capsule 

 and containing a liquid, semiliquid or gelatinous material. Cysts 

 are not true tumors. However, a tumor may become cystic, 

 (Cystoma.) and the capsule surrounding a cyst may proliferate 

 and become a true tumor. Collections of inflammatory and oede- 

 matous fluids, are not usually considered as cysts. Cysts may 

 be single or multiple. The 'latter are designated multilocular 



cvsts. 



■ Cause. Cvs's mav be caused bv, 1. obstruction of gland ducts, 



thus favo-in- p-c'.-mula*ion ?"d retention of a normal secretion 



