EXOSTOSES, OR BONY TUMOUKS. 493 



HYDROCEPHALUS DROPSY OF THE BRAIN. 



The arachnoid, or serous membrane covering the brain, 

 is not unfrequently the seat of an unnatural accumulation 

 of clear watery liquid. This is not uncommonly seen in 

 newly born animals, and especially in calves and puppies. 

 Connected with this chronic cranial dropsy, there is mal- 

 formation of the cranial bones. Many detached points of 

 ossifications are seen in the broad membrane covering the 

 encephalon ; and if this is pressed upon, the brain is affected 

 and the animal injured, and perhaps destroyed. In the 

 majority of instances the animals die. In adult animals 

 hydrocephalus is rare, except as it occurs in sleepy staggers. 

 Sheep, with sturdy, are said to die of hydrocephalus, or 

 water in the head ; but it is well known that the cyst dis- 

 tended with fluid in this disease is of specific parasitic 

 origin. 



The cases of hydrocephalus in newly-born animals are 

 usually, if not always fatal. 



TUMOURS IN THE CRANIAL CAVITY. 



A variety of products are developed in the cranial cavity 

 with very different degrees of rapidity, and therefore in- 

 ducing disorders of an acute or chronic character according 

 to the conditions under which they are formed. The 

 growths are either abnormal formations from the inner sur- 

 face of the cranial bones or in the substance of the brain. 



EXOSTOSES, OR BONY TUMOURS. 



These are met with most frequently in cattle, and con- 

 sist in hard, enamel-like products of the inner plate of the 

 scalp, occasionally no larger than a bean, and some occa- 

 sionally attaining the dimensions of a turkey's egg. These 



