32 



ANATOMY AND PHYSIOLOGY OF 



thinner than the anterior, and has several 

 foramina through it — three or four of 

 large size — which transmit vessels to the 

 frog. 



" The False Cartilages. — From the in- 

 ferior and posterior sides of the true carti- 

 lages, proceed in a direction forward — 

 towards the heels of the coffin-bone — two 

 fibro-cartilaginous productions, to which 

 Mr. Coleman has given the name of ' infe- 

 rior cartilages.' If they are to be consid- 

 ered as cartilages at all, I prefer denomi- 

 nating them false ; they being, as well in 

 structure as in use, different from the true 

 or lateral cartilages. They spread inwards 

 upon the surface of the tendo perforans ; 

 become united at their inner sides with the 

 superior margin of the sensitive frog ; are 

 covered inferiorly by the sensitive sole ; and 

 at the same time assist in the support of 

 the sensitive frog. They are triangular in 

 their figure, and are arched in the same 

 manner as the sole. 



" Use. — Their use appears to me to be, 

 to fill up the triangular vacant spaces left 

 between the tendo perforans and heels of 

 the coffin-bone, thereby completing the sur- 

 face of support for the sensitive frog, and 

 extending that for the expansion of the 

 sensitive sole. Bone in these places must 

 have proved inconvenient by more or less 

 impeding the impression upon, and con- 

 sequent reaction of, the sensitive frog. 



"the sensitive lamina or lamella. 



" So is denominated the laminated, mem- 

 branous, vascular structure clothing the wall 

 of the coffin-bone. 



" Production. — The sensitive laminas 

 appear to be derived from the coronary sub- 

 stance — the one, in fact, seems to be a con- 

 tinuation from the other ; for if, in a foot in a 

 putrid condition, we attempt to part them 

 by force, we may make an artificial rent 

 somewhere, but can find no natural separa- 

 tion between them. The cuticular covering 

 of the coronary substance having descended 

 upon the coffin-bone, the circumference of 

 which is less than that of the coronet, be- 

 cause thereupon gathered into numerous 



fittle plaits or folds, which proceed in paral- 

 lel slanting lines down the wall of the bone : 

 a transformation it may be difficult to ex- 

 plain, since the lamina? unfolded would 

 occupy a much larger surface than the 

 coronet ; at the same time, it is one that 

 has its parallels in the animal constitution, 

 and a remarkable one in the instance of the 

 ciliary processes. 



" Division. — According to this mode of 

 derivation, every lamina consists of one 

 entire plait or duplication of substance, 

 having its imvard sides intimately and in- 

 separably united ; its outivard sides being 

 the surfaces of attachment for the horny 

 lamiuEB. It has also two borders : one op- 

 posed to the coffin-bone, the other to the 

 hoof ; and two ends or extremities, one issu- 

 ing out of the coronary substance, the 

 other vanishing in the sensitive sole. 



" Structure. — The substance of the la- 

 minae when held to the light evinces a 

 degree of transparency ; although its nature 

 is extremely dense, and it possesses extra- 

 ordinary toughness and tenacity. Veteri- 

 nary writers and lecturers have endowed 

 the laminae with a high degree of elasticity : 

 but it appears to me that the property 

 is referable to their connections, and not 

 one that is inherent in their own sub- 

 stance. 



" Elastic Structure. — This is a substra- 

 tum of a fibrous periosteum-like texture, 

 attaching the laminae to the coffin-bone, in 

 which it is that the property of elasticity 

 resides to that remarkable extent usually 

 ascribed to the laminae themselves : indeed, 

 so elastic is it found to be, that it can be 

 made to stretch and recede the same as a 

 piece of India rubber. Its fibres take a 

 direction downward and backward. At 

 the same time, it affords a commodious bed 

 for the ramification of blood-vessels issuing 

 from the substance of the bone, in which 

 they are (particularly in the stretched con- 

 dition of the substance) protected from in- 

 jurious compression and consequent inter- 

 ruption to their circulation. 



" Number. — In round numbers we may 

 estimate the laminae at about 500 ; not in- 



