264 THE ANATOMY AND 



behind the coffin bone it becomes thicker, and attaches 

 itself to the inferior cartilages. The sensitive sole upon 

 its upper surface is of a ligamentous nature, but the 

 underneath is vascular ; and from it is secreted the horny 

 sole. The vascularity of this part renders it very suscepti- 

 ble of inflammation. The sensitive frog presents a very 

 curious structure of ligamentous and tendinous expansions 

 above ; but covered underneath by a horny coating, 

 corresponding in shape to the sensitive frog, and secreted 

 from it. It lies in an interval within the sensitive sole, 

 attached by its point to the inferior surface of the coffin 

 bone, with its heels expanding posteriorly ; being a con- 

 tinuation of the secretive coronet, and attached to the 

 cartilaginous substance, imited with cellular and fluid mat- 

 ter. The lateral cartilages (see Plate X. Fig 2.6, c) , 

 one to each side, are fixed into a groove, upon the upper 

 surface of each wing of the coffin bone. Independent of 

 their bony attachment, they are also retained in their situa- 

 tion by means of ligamentous fibres, and by lateral con- 

 nexions. They are externally convex, internally they are 

 concave ; highest in the centre, but thinner and smaller 

 towards the extremities : their inferior portions pass under 

 the wings of the coffin bone, and unite with the semi-car- 

 tilaginous substance of the elastic frog. The lateral car- 

 tilages are partly within and partly without the hoof; 

 are covered at their lower portion by the coronary liga- 

 ment, which, by being extended over them, prevents their 

 too great dilatation. To the low^er part of their external 

 surface the laminae gain an attachment ; and within their 

 internal portion is lodged the substance forming the upper 

 and posterior part of the elastic frog (see Plate X. 

 Fig 2 . «, h). The uses of these cartilages, as before ob- 

 served, are considerable, and divested of them the coffin 

 bone appears but small, compared to the hoof that en- 

 closes it ; but, increased by the attachment of the car- 

 tilages, the whole is made more proportionate, equally 

 useful for support as though they were altogether bony, yet 

 yielding and elastic. The cartilages themselves appear 

 particularly intended to operate in expanding the upper 

 horny portions of the hoof; and they also assist in the 

 preservation of the cavity of the coffin joint. 



