30 



ANATOMY AND PHYSIOLOGY OF 



appear to have any power in impairing its 

 texture, or, at least, in dissolving it. Liquor 

 potassEB will not only turn it black, but will 

 corrode the horn of the hoof. Ammonia 

 does not change its color, but slowly destroys 

 its texture, rendering it brittle and rotten. 



"INTERNAL PARTS OF THE 

 FOOT. 



" The internal, sensitive, organic parts of 

 the foot, comprise the bones, ligaments, ten- 

 dons, coronary substance, cartilages, sensitive 

 lamince, sensitive sole, and sensitive frog. 



" The bones entering into the composition 

 of the foot are the coffin and navicular 

 bones : to which may be added (as forming 

 part of the coffin-joint, and consequently 

 having intimate relation to them), the coro- 

 net bojie. 



" The tendons immediately connected 

 with the foot are those of the extensor pedis 

 and the flexor pedis perforans : the former 

 being inserted into the coronal process ; the 

 latter into the posterior concavity of the 

 coffin-bone. 



"the coronary substance. 



" A less inappropriate name for the part 

 commonly called the coronary ligament* 



" To revert, for the sake of elucidation 

 here, to former description --nfter the hoof 

 has been detached by a process of macera- 

 tion or putrefaction, in a perfectly entire, 

 uninjured condition, it presents around its 

 summit a circular groove, bounded in front 

 by a soft whitish substance, having a thin 

 edge, and being of a nature between horn 

 and cuticle ; and behind, by an attenuated 

 margin, more horny in its character, whose 

 thin edging is denticulated or serrated. Into 

 this circular groove or canal is received the 

 terminating margin of the cutis : the cuti- 

 culo-horny layer of the hoof, in front of it, 

 having every appearance of being a continu- 

 ation of the cuticle. 



" Situation — Dimension. — The coronary 



* Averse as I am to changing or altering names, noth- 

 ing less than a palpable contradiction, in regard both to 

 structure and function, would have induced me to do so in 

 the present instance. 



substance occupies the concavity formed 

 upon the inside of the superior or coronary 

 border 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 sub- 

 stance around its middle and most promi- 

 nent parts, growing gradually thinner both 

 above and below. 



" Connection. — Externally, the coronary 

 substance is connected with the hoof; and 

 the connection appears to be principally, if 

 not entirely, of a vascular nature : the sur- 

 face of the wall presenting a porous honey- 

 comb-like texture, and the villi or vessels 

 issuing from the coronary substance enter- 

 ing the pores, and thus establishing an inti- 

 mate and extensive vascular union between 

 these organic and inorganic parts. Inter- 

 nally, the coronary substance is connected 

 with the coffin-bone, the extensor tendon, 

 and the cartilages, by a fine, dense, copious 

 cellular tissue, which at the same time forms 

 a bed for the assemblage and ramification of 

 the blood-vessels concerned in the secretion 

 of the wall of the hoof. Superiorly, its 

 union with the skin is so intimate and com- 

 plete, that one has been thought to be a 

 continuation 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 demar- 

 cation between them, but discover such 

 difference of internal structure as forbids 

 the adoption of this delusive notion. As it 

 descends upon the coffin-bone, the coronary 

 substance not only grows thinner, but in 

 growing attenuated becomes imperceptibly 

 gathered or puckered into numerous points, 

 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 transfor- 

 mation takes place is smaller in circumfer- 

 ence than the coronet; consequently the 



