268 OF HYDATIDS. 



lar stimulus, which hydatids, as living animals, 

 give, the organ containing them, or to which they 

 are attached, undergoes still further changes, ia 

 consequence of an action excited ; which perhaps 

 may not improperly be termed specific: in proof 

 of which, the organs, witliin which hydatids are 

 contained, or to which they are attached, are soon- 

 er, and to a much greater degree aft'ected, than by 

 the ordinary fixed dropsical cysts, whether of the 

 natural or preternatural kind. Thus a large quan- 

 tity of water, accumulated in the ventricles of the 

 brain in hydrocephalus internus, sometimes occa- 

 sions in an infant a disunion of the bones of the 

 cranium from each other, and the head attains an 

 unnatural bulk. No part of the cranium becomes 

 soft, thin, or is absorbed. But if hydatids are lodg- 

 ed in one of the ventricles of the brain, (which is 

 not uncommon in sheep,) the cranium over that ven- 

 tricle becomes soft, and may be cut without turn- 

 ing the edge of. the knife, and loses considerably 

 of its thickness, and in some cases holes are form- 

 ed in it, though t!ie dura mater remains entire be- 

 tween the cranium and the brain ; and even though 

 the cyst, containing the hydatids, is still covered 

 by a seemingly sound portion of the brain, and [»ia 

 mater. The same happens in the human body; 

 for in the first case stated, where an hydatid of the 

 size of a goose's egg was found in the right ven- 

 tricle of the brain of a man, covered by a gelati- 

 nous matter, without any fibrous adhesion to the 

 membrane lining the ventricle, the cranium was 



