DISEASES OF THE BRAIN. 69 



OOMPRESSIOW OF THE BRAIN. 



Cysts containing a serous or viscid fluid, are occasionally found 

 within the cranial cavity, and lying upon or imbedded in the 

 brain. The following is a history of a case of this kind : — A 

 horse exhibited symptoms of vertigo, or staggers, which disap- 

 peared after copious bleeding and purgatives. About twelve 

 months afterwards the same complaint was evident. He carried 

 his head low and inclined to the right side. He staggered as he 

 walked, and the motion of his limbs was marked by a peculiar 

 convulsive action, confined to the four extremities. He moved 

 by a succession of spasmodic boundings. He was completely 

 deaf; andrapidly lost flesh, though he ate and drank voraciously. 

 He remained in this state, to the shame of the owner and the 

 practitioner, several months, and then he had a fresh attack of 

 vertigo, and died suddenly. On examination of. the brain, its 

 membranes were foimd to be completely reddened ; and, between 

 the two lobes of the brain, was a round cyst as large as a pullet's 

 egg. The pressure of this was the mardfest cause of the mis- 

 chief. 



PRESSURE ON THE BRAUf. 



This may be produced by some fluid thrown out between the 

 membranes, or occupying and distending the ventricles of the 

 brain. In the fuU-grown horse it rarely occurs ; but it is well 

 known to breeders as an occasional disease of the foal, under the 

 name of " water in the head." The head is either much en- 

 larged, or stangely deformed, or both ; and the animal dies, either 

 in the birth, or a few days after it. 



MEGRMS. 



This is another kind of pressure on the brain, resulting from 

 aji unusual determination or flow of blood to it. From various 

 causes, of which the most common is violent exercise on a hot 

 day, and the horse being fat and full of blood, more than the 

 usual quantity is sent to the head ; or, from some negligence 

 about the harness — as the collar being too small, or the curb- 

 rein too tight — the blood is prevented from returning from the 

 head. The larger vessels of the brain wiU then be too long and 

 injuriously distended ; and, what is of more consequence, the 

 small vessels that permeate the substance of the brain wiU be 

 enlarged, and the bulk of the brain ■ increased, so that it will 

 press upon the origins of the nerves, and produce, almost without 

 warning, loss of power and consciousness 



