OF HYDATIDS. 257" 



©pening, of a pearly or yellowish colour, contain- 

 ing a watery fluid, and often a number of smaller 

 hydatids, included within its proper capsule or 

 cyst. 



" Hydatids are of very different sizes ; some are 

 not larger than a millet seed, others are equal in 

 bulk to an ox's bladder. The coats of hydatids 

 are generally thin and semi-transparent, though 

 sometimes so thick as to be perfectly opaque. The 

 habitat (to make use of the expression of modern 

 naturalists) of hydatids is also different. 



^^They have been discharged by vomiting, and 

 by stool ;* frequently they are attached to the pe- 

 ritonaeum, and especially to that part of it which 

 covers the liver, or they are imbedded in that or- 

 gan, or attached to the kidneys or ovaria, or to 

 some part of the alimentary canal. 



^^ Hydatids have also, though more rarely, 

 been found in the cellular membrane, likewise be- 

 tween the muscles, and sometimes; though still 

 more rarely, within the bones. 



"There formerly existed a great variety of 

 opinion respecting the nature of hydatids. Natu- 

 ralists now seem to agree, that they belong to the 

 animal kingdom, and constitute a genus of animals, 

 of which there are several species ; but sufficient 

 observations on recent or living hydatids have not 

 yet been made, to enable us to draw up generic or 



* See Philosophical Transactions, vol. wn, 

 33 



I 



