43 



copied from each other, without examining for themselves, the 

 error was perpetuated until Mr. Percival demonstrated that 

 ' the elasticity was not inherent in the laminae but in the sub- 

 stance connecting them with the coffin-bone which possesses 

 highly elastic properties, and affords a convenient bed for the 

 numerous blood-vessels which secrete the laminae." 



AN UNDETERMINED QUESTION. 



In this connection the late Prof. Spooner, in the course of 

 his lectures, stated substantially as follows : " The precise 

 nature of the union between the vascular and horny laminae 

 is not yet established. I believe it will be found upon more 

 extended microscopic investigation to be similar to, if not iden- 

 tical with that of the chorion of the foetus, and the tunica decidua 

 uteri of the uterus. The same kind of union also exists between 

 the dermis and epidermis. Whatever doubts may exist as to 

 the histological character of this union, what is certainly known 

 is that the union is a vascular and vital, not a mechanical one, 

 and that it is one of extreme delicacy, and ill-calculated to 

 bear the tremendous burden the weight of the animal would 

 impose upon it." 



THE INTERPERIOSTEAL PAD. 



It will not be difficult to perceive where this apparent power 

 of elongation comes from, when the peculiar structure of the 

 periosteum of the coffin-bone is fully comprehended. As shown 

 by Percival it is a double membrane, the union of which is 

 attached to the irregular surface of the coffin bone, and the 

 outer presents a plaited or frilled surface. Between this inner 

 and outer membrane, a layer of elastic material is interposed,, 

 which, like most other structures of the foot, answers a two- 

 fold purpose. It furnishes a nidus or bed for the safe repose 

 of the vessels and nerves that ramify upon the laminae, and 

 particularly those which are engaged in the work of secreting, 

 the horny laminae. The frilled or laminated arrangement 

 affords abundance of space for these vessels and nerves as they 



