THE HOESE. 



31 



same measure of coronary substance which 

 but tensely and smoothly covered the latter, 

 admitted of being disposed in gathers or 

 folds so soon as it reached the former. Pos- 

 teriorly, the coronary substance forms a 

 junction, indeed becomes continuous in 

 substance, with the heels of the sensitive 

 frog. 



" Structure. — The coronary substance 

 discloses three different parts in its com- 

 position : 1. A fibro-cartilaginous circling 

 band, forming the substratum and basis of 

 the entire structure. 2. A cuticular cover- 

 ing, so called from its resemblance in tex- 

 ture to the cutis. 3. A network of blood- 

 vessels, reposing upon the former, and 

 covered by the latter. The cartilaginous 

 structure, freed from its vascular connec- 

 tions, is found to be wrought in the form 

 of a coarse, open, irregular network, and 

 appears designed mainly for the purpose of 

 affording a bed for the lodgment and rami- 

 fication of the blood-vessels destined to pror 

 duce the wall. The looseness of its con- 

 nection, added to its own elasticity, renders 

 this substance peculiarly adapted to accom- 

 modate itself to the motions of the coffin- 

 joint, and thus preventing those movements 

 from operating prejudicially to the super- 

 imposed glandular structure. 



" Organization. — The coronary sub- 

 stance may be ranked among the most vas- 

 cular parts of the body : no gland even 

 possesses, for its magnitude, a greater abun- 

 dance of blood-vessels, or of blood-vessels 

 (taking them generally) of larger size ; nor 

 does there exist any part in which greater 

 care appears to have been taken to arrange 

 its vessels so as to insure an uninterrupted 

 supply of blood. These vessels it is that 

 produce the wall : and there is every reason 

 to believe that they perform this office 

 without any assistance from the vessels of 

 the laminae. 



" THE CARTILAGES 



" Are two broad, scabrous, concavo-con- 

 vex, cartilaginous plates, erected upon the 

 sides and wings of the coffin-bone. Pro- 

 fessor Coleman calls them ' the lateral car- 



tilages,' in contradistinction to two others 

 he has named ' the inferior cartilages.' 



" Situation. — The cartilages form the 

 postero-lateral parts of the sensitive foot, 

 extending the surface considerably in both 

 these directions. 



" Attachment. — The cartilages are fixed 

 into fossa? excavated in the supero-lateral 

 borders of the coffin-bone. Their anterior 

 parts become united, on each side, with 

 descending lateral expansions from the ex- 

 tensor tendon, and are also attached to the 

 coronet bone by cellular membrane. Their 

 posterior parts surmount the al(B or wings 

 of the bone, to which they are firmly fixed, 

 and from which they project backwards, 

 beyond the bone, giving form and substance 

 to the heel. Supposing one of the carti- 

 lages to be divided into two equal parts by 

 a line drawn horizontally across its middle, 

 the superior half, which extends as high as 

 the pastern-joint, is covered by skin only; 

 and on that account is quite perceptible to 

 the feel, and (in form) to the sight, as the 

 animal stands with his side towards us. 

 The lower half is covered, superiorly, by 

 the encircling coronary substance ; inferiorly, 

 by sensitive laminae : consequently, over all 

 by the hoof, which envelopes both the coro- 

 nary substance and the laminae. The ex- 

 treme posterior ends of the cartilages incur- 

 vate downward and backward ; but, being 

 overreached by the heels of the sensitive 

 frog, any abrupt or exposed termination of 

 them is prevented. Around these points 

 also the coronary substance makes its in- 

 flections upon the sensitive frog, thereby 

 giving them additional substance and sup- 

 port. 



" Form. — Considered in the detached 

 state, the cartilage in its general figure de- 

 scribes an irregular quadrangle, of which 

 the supero-anterior and infero-posterior an- 

 gles are the most projecting ; the latter at 

 the same time being incurvated inwards. 

 Externally, the cartilage is pretty regularly 

 convex; internally, it is unevenly concave, 

 the surrounding border turning inwards into 

 the substance of the sensitive frog. The 

 posterior part of the cartilage is somewhat 



