438 PLANTAR SYSTEM. 



To revert, for the sake of elucidation here, to former descrip- 

 tion — after the hoof has been detached by a process of maceration 

 or putrefaction, in a perfectly entire, uninjured condition, it pre- 

 sents around its summit a circular groove, bounded in front by 

 a soft whitish substance, having a thin edge, and being of a na- 

 ture between horn and cuticle ; and behind, by an attenuated 

 margin, more horny in its character, whose thin edging is denti- 

 culated or serrated. Into this circular groove or canal is received 

 the terminating margin of the cutis; the cuticulo-horny layer of 

 the hoof, in front of it, having every appearance of being a con- 

 tinuation of the cuticle. 



Situation — Dimension. — The coronary substance occupies the 

 concavity formed upon the inside of the superior or coronary bor- 

 der of the wall of the hoof: it is the part constituting the basis 

 of the circular prominence commonly distinguished in the living 

 animal as the coronet. It is broadest around the toe of the wall, 

 diminishing in breadth towards the quarters and heels, and 

 being somewhat broader around the outer than the inner side. 

 It is thickest in substance around its middle and most promi- 

 nent parts, growing gradually thinner both above and below. 



Connexion. — Externally, the coronary substance is connected 

 with the hoof; and the connexion appears to be principally, if 

 not entirely, of a vascular nature: the surface of the wall pre- 

 senting a porous honeycomb- like texture, and the villi or ves- 

 sels issuing from the coronary substance entering the pores, and 

 thus establishing an intimate and extensive vascular union be- 

 tween these organic and inorganic parts. Internally, the coro- 

 nary substance is connected with the coffin-bone, the extensor 

 tendon, and the cartilages, by a fine, dense, copious cellular tis- 

 sue, which at the same time forms a bed for the assemblage and 

 ramification of the bloodvessels concerned in the secretion of the 

 wall of the hoof. Superiorly, its union with the skin is so in- 

 timate and complete, that one has been thought to be a conti- 

 rmation of the other; and, so far as meets the eye of a common 

 observer, they might be taken as such : but, when we come to 

 examine them by anatomical tests, we not only find a line of 

 external demarcation between them, but discover such difference 

 of internal structure as forbids the adoption of this delusive no- 

 tion. As it descends upon the coffin-bone, the coronary substance 

 not only grows thinner, but in growing attenuated becomes im- 

 perceptibly gathered or puckered into numerous pomts from 

 which issue a like number of plaits or folds, which afterwards 

 form the sensitive laminae. It is worthy of remark, that the part 

 of the bone upon which this transformation takes place is smaller 

 in circumference than the coronet; consequently the same mea- 



