CHOI^ESTEATOMA. 



These are tumors formed largely of the peculiar fat which is 

 found- in bile and brain matter, and that crystallizes in flat oblong 

 scales with a notch at one corner. -The tumors are usually con- 

 nected with the choroid plexus and developed beneath the pia 

 mater, and may be of any size from a pea to a hen's egg, or in 

 exceptional cases a sheep's kidney. As a basis there is a stroma 

 of connective tissue permeated by bloodvessels from the plexus. 

 Groups of spherical or polygonal cells fill the interstices while 

 fusiform cells are found in the stroma. There is a variable 

 amount of phosphate or carbonate of lime which in oldstanding 

 cases may give a cretaceous character to the mass. These consti- 

 tute sandy tumors (psammomata). 



Cholesteatomata are especially common in old horses and are 

 manifestly connected with congestion of the choroid plexus and 

 exudation. In a recent case or in a case which has shown a recent 

 cerebral hyperaemia, we may find a central mass of yellowish 

 cholesterine, and surrounding this an abundant yellow gelatinoid 

 exudation. This latter is rich in cholesterine which fails to dis- 

 solve along with the rest of the exudate on the occurrence of 

 resolution, and is therefore laid up as the solid fatty material. 

 For the same reason the fatty element is usually laid on in layers, 

 one corresponding to each access of local hyperaemia and exuda- 

 tion. The great tendency to calcareous degeneration has been 

 attributed to the abundance of phosphate of lime in the cerebral 

 exudate. 



The symptoms of these tumors are exceedingly uncertain. 

 Many such tumors of considerable size have been found after 

 death in animals in which no disease of the brain had been sus- 

 pected during life. In these it is to be inferred that the accretions 

 were slow, gradual, and without any serious congestion. In 

 other cases the tumor is attended by paroxysms of vertigo, or in- 

 dications of hypersemia or meningitis, which will last for several 

 days and gradually subside. It is reasonable to suppose that the 

 tumors are largely the result of such recurrent attacks of en- 

 cephalitis, and are no less the cause of their recurrence. The 

 9 129 



