PLANTAR SYSTEM. 441 



l^he Sensitive LumintB or Lamellce. 



So is denominated the laminated, membranous, vascular struc- 

 ture clothing the wall of the coffin-bone. 



Production. — The sensitive laminae appear to be derived from 

 the coronary substance— the one, in fact, seems to be a continua- 

 tion 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 separation between them. 

 The cuticular covering of the coronary substance having descend- 

 ed upon the coffin-bone, the circumference of which is less than 

 that of the coronet, because thereupon gathered into numerous 

 little plaits or folds, which proceed in parallel slanting lines down 

 the wall of the bone : a transformation it may be difficult to ex- 

 plain, since the laminae 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 inward sides intimately and inseparably united ; its outward 

 sides being the surfaces of attachment for the horny laminae. It 

 has also two borders; one opposed to the coffin-bone, the other 

 to the hoof: and two ends or extremities, one issuing out of the 

 coronary substance, the other vanishing in the sensitive sole. 



Structure. — The substance of the laminae when held to the light 

 evinces a degree of transparency ; although its nature is ex- 

 tremely dense, and it possesses extraordinary toughness and tena- 

 city. Veterinary writers and lecturers have endowed the laminae 

 with a high degree of elasticity : but it appears to me that the 

 property is referrible to their cotinexions, and not one that is in- 

 herent in their own substance. 



Elastic Structure. — This is a substratum of a fibrous perios- 

 teum-like texture, attaching the laminae to the coffin-bone, in 

 which it is that the property of elasticity resides to that remark- 

 able 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 Indian rubber. Its fibres take a 

 direction downward and backward. At the same time, it affords 

 a commodious bed for the ramification of bloodvessels issuing 

 from the substance of the bone, in which they are (particularly 

 in the stretched condition of the substance) protected from in- 

 jurious compression and consequent interruption to their circula- 

 tion. 



Number. — In round numbers we may estimate the laminae at 



3 L 



