HYDATIDS IN THE BRAIN. 227 



selves to the coats of the intestines, while they suck the juices 

 therefrom. These heads increase by a process of budding, and 

 often amount to dozens, and sometimes hundreds hi number. The 

 pressure exerted by these bladders upon the brain, produces the 

 peculiar symptoms exhibited, and the act of turning to one side or 

 the other, helps to determine the seat of the hydatid in the body 

 of the brain, which 

 is found to be on 

 that side to which 

 the sheep turns. 

 The natural histo- 

 ry of this parasite 

 is as follows : 

 When the head of 

 a sheep, containing 



the bladder-worms Fi g^^^g MAGNIFIEI) . 



of this species, is 



devoured by a dog, the larvae are transformed within him into 

 tape-worms. This worm (tcenia ccenuri^s) at maturity, or its eggs, 

 being voided by the dog upon the grass of a pasture, are swallowed 

 by the sheep, are hatched in its stomach, and penetrate all parts 

 of the body, perishing everywhere except in the brain, which is 

 its usual habitation. There they develop, remaining dormant, 

 until chance favors their round again. Old sheep are rarely 

 affected by this parasite, the lambs suffer chiefly from them. One 

 infested dog will void thousands of eggs which not only escape 

 with the dung, but being attached to the anus, are carried about 

 and dropped in a multitude of places. 



To prevent the spread of this parasite, it is necessary only to 

 prevent the heads of 'affected sheep from being devoured by dogs 

 or hogs, or to keep dogs from the pastures. The heads of sheep 

 dying from the disease should therefore be burned, and not thrown 

 out. The treatment of sheep subject to the parasite consists in an 

 operation by which the skull is pierced and the bladder punctured, 

 when the water in it escapes and is absorbed, leaving the worm to 

 perish. The pressure and irritation upon the skull causes some 

 absorption of its substance, and a soft spot is caused over the blad- 

 der. This may be easily felt by pressure of the finger. A curved 

 awl may then be inserted through the skull and the bladder pierced ; 

 or by means of a tubular saw (or trephine), a round piece of bone 

 is cut out of the skull, a flap of the skin first being laid back, and 

 the bone being lifted, the bladder is laid bare and removed. The 

 skin is relaid and held in place by a stitch or plaster, and the 



