294 



THE HORSE. 



their surface of a plasma, in which rounded cells develop them- 

 selves, in correspondence with the villi fioui which the secretion ia 

 poured out. These cells are arranged in layers, corresponding 

 with the secretory surface. In the crust this growth takes place 

 from the superior border to the inferior, but in the sole and frog, 

 from the internal surface to the external. This growth is constant 

 through the life of the animal, and it would give the hoof an 

 excessive development if it were not either for the wear of the soil 

 in the unshod horse, or of the action of the smith's knife in the 

 shod one ; but the increase of the wall being solely from above 

 downwards, it does not require any reduction on its external sur- 

 face. The coronary substance, sometimes called the coronary liga- 

 ment, is a fibro-cartilaginous band intervening between the skin of 

 the leg and the hoof, covered 

 with cuticle externally, and with 

 villi, which form a secretory sur- 

 face on the edge towards the 

 hoof. It is most liberally sup- 

 plied with blood, as we shall 

 presently see, and is attached to 

 the upper part of the coflBn bone 

 and extensor tendon by cellular 

 tissue. It gradually becomes 

 thinner as it descends upon the 

 pedal bone, and ends in puckers 

 or folds, which are continuous 

 with those of the laminae, and 

 are not even separable from then: 

 by maceration. The laminse 

 thus continuing upon the pedal 

 bone, consist of about five hun- 

 dred parallel folds or plaits, 

 plentifully supplied with blood, 

 and forming a secretory surface, 

 which aids the coronary suo- 

 stance to foi'ui the horn. They 

 lie upon an elastic substraxuiu 

 of fibrous periosteum, which ib 

 of great service in taking oft the 

 jar from the foot in its bauer- 

 Fu 16.— VIEW OP VESSELS OP THE FOOT, IN- iflg upou hard Toads, for It ap- 

 i. Plantar vein. pears that the Weight of the 



2. Plantar artery. bodv is suspended fruni these 



8. Brnnflies to tlie coronary substance and i , j j. • ^ ..i 



iiimii,,,.. plates, and not carried upon the 



i Poste, i.,r djvi8i<,n of plantar artery. gole. The laminae are contidu- 



5. Perpendicular branch. ■ i i .. i 



6. Anastumosis witli opposite plantar artery. OUS at the tOC With the Sensible 



