OF HYDATIDS. 26S 



*^ Of the Coats of Hydatids. 



" The coats of the hydatid are not of a uniform 

 density, being much thicker in some than in oth- 

 ers ; and even in the same hydatid, we generally 

 observe some portions of these coats of greater den- 

 sity than others ; so that in the same hydatid, there 

 is a difference as to transparency or opacity in the 

 different parts of its coats. 



^^ Hydatids have two coats, an outer and inner, 

 and the outer coat is considerably thicker than the 

 inner. There are no filires in the outer coat of an 

 hydatid visible to the naked eye ; yet the outer coat 

 possesses the distinguishing character of a muscle, 

 the power of contraction on the application of a 

 stimulus. The inner coat is very thin, semi-trans- 

 parent, soft, pulpy, and very tender, and in very 

 large hydatids possesses a small share of elasticity. 

 The interior surface is lubricated by a fluid, which 

 renders it slippery to the touch. From the inner 

 side of some of the larger hydatids, there are several 

 excrescences, which are made up of a congeries of 

 very sm ill hydatids, and the size of these bears a 

 ratio to the size of the hydatid. 



'^ These excrescences are retained in their situa- 

 tion by a very thin transparent membrane, which 

 covers them. There is still another appearance, 

 which I have remarked, namely — a number of small 

 cells, formed by folds of the inner membrane of the 

 large pregnant hydatid, containing the smnll ones. 



