SOLIPEDA. 



739 



The wings or lateral processes above de- 

 scribed, as extending from the base of the frog, 

 not only enclose the posterior ends or doub- 

 lings in of the hoof, but the same horn is con- 

 tinued around the whole upper edge or margin 

 of the roof, forming a broad convex band, 

 whose upper edge, projecting higher than the 

 hoof itself, receives and covers over the ter- 

 minating edge of the skin, where it meets the 

 hoof, and thus protects this part from external 

 injuries, to which it would otherwise be liable. 

 Posteriorly it is of considerable breadth, and 

 firmly connects the frog with the upper part 

 of the slope of the horny heels, over which it 

 likewise expands. This structure, first de- 

 scribed by Bracy Clark, received from him the 

 denomination of the " coronary frog-band." 



In the centre of the frog, as viewed from 

 the sole, is a considerable cavity, the edges of 

 which are furnished with rising lips or promi- 

 nent margins of the horn ; this hollow is 

 termed the cleft of the frog, and extends to a 

 considerable depth. This cavity appears to 

 serve the following useful purposes * : 1st. 

 It is a safeguard from rupture between the 

 two halves or divisions into which the foot 

 is almost separated. 2dly. By closing when 

 pressure comes direct upon the underside 

 of the foot, it prevents too much condens- 

 ation of the horn at this part, and con- 

 sequent pressure and a too solid resistance 

 upon the soft parts beneath. 3dly. When 

 the foot bears partially upon the ground, as by 

 one side only, which will happen occasionally 

 where the surface is irregular, it can extend 

 along with that side of the foot without rup- 

 turing, by the greater liberty it thus affords to 

 the part, while at the same time the strength 

 of its margin secures it from laceration. 4thly. 

 On loose soils this indent or cavity will doubt- 

 less assist in giving the foot a firmer hold by 

 the irregularity it offers to the surface. 



It is, however, upon the inner aspect of the 

 hoof that the most remarkable part of this 

 structure is to be observed, for when ex- 

 amined internally it is found that the external 

 cleft is only the hollow base of a cone of stout 

 horn of considerable size, which passes from 

 it directly into the substance of the sensitive 

 frog, and which, though completely imbedded 

 in the soft parts, is nearly or quite as hard 

 and tough as is the horn of the exterior of the 

 frog which is exposed to the air. This re- 

 markable provision seems to serve the pur- 

 pose of uniting more firmly the two halves of 

 which the foot of the solipeds at this part 

 really consists, there being here an evident 

 tendency, in the tegumentary defences of the 

 horse's foot, towards that division which in 

 the ruminating quadrupeds is completely 

 carried out. This important cone of horn 

 Bracy Clark named the frogstay or bolt, ob- 

 serving that, like an inserted tooth, it more 

 firmly holds the horny to the sensitive frog, 

 for while the sensitive frog falls into the in- 

 verted arch of the horny frog, and is thus 

 held most firmly in its place, this part, entering 



* Bracy Clark, op. cit. 



in the opposite direction into the sensitive 

 frog, serves reciprocally to confirm and fix 

 these parts together, and preserve them from 

 external injury and dislocation. An excel- 

 lent view of this piece of anatomy is obtained 

 by making a perpendicular section of the foot 

 extending through the "heels and surrounding 

 elastic matter." 



The Sole. This is an irregular plate of 

 horn, which serves to close up the space or 

 great inferior opening described by the lower 

 circumference of the wall, and makes the 

 third member or part of the hoof. It is 

 usually of an arched form, more or less flat- 

 tened, its concavity being turned to the ground, 

 so that its centre, which is the thinnest part, 

 is by this means removed from the degree of 

 external pressure which the sides or bottom 

 part of the arch have to support. 



Nature has secured herself, by the arrange- 

 ment of this part, in two ways from the re- 

 sistance which an arch of common properties 

 would create on becoming condensed under 

 pressure, and forcibly resisting the load 

 brought upon it, which would have been sub- 

 versive of the leading principles of the me- 

 chanism of the hoof. In the first place the 

 sole being cleft to its centre or beyond it by 

 the large triangular opening formed at its 

 posterior part, which, destroying the resist- 

 ance of the arch, serves to receive the ends 

 also of the wail of the hoof first, and is then 

 closed and filled up by the inverted arch of 

 the frog ; so that the ends of the hoof are 

 thus tied in and secured from being forced 

 asunder by the pressure from within, being 

 thus wedged in between the frog and the sole, 

 serving in their places the other offices already 

 noticed, while the sole, being thus broken, has 

 a diminished resistance in the centre. 



Again : the lower circumference of the arch 

 of the sole is everywhere found abutting 

 against the sides of the wall, which are ren- 

 dered sufficiently flexible outwards to yield to 

 the weight when pressed against by the de- 

 scent and flattening of the sole, so that every 

 provision for the elasticity of the foot is thus 

 fully secured. 



The horse's hoof is therefore fully provided 

 with the means of preserving its form ; but 

 this power is unfortunately grievously inter- 

 fered with by the process of shoeing ; and it 

 is in this country at least a very rare occur- 

 rence to obtain an opportunity of examining a 

 foot in its full-grown natural condition. 



From the above description of the foot of 

 the horse it will be seen that, although when 

 viewed in front it appears to be solid and 

 single, the terms Solidungula and Solipes con- 

 vey but a very imperfect notion of the real 

 nature of this kind of hoof; for though the 

 front be solid the posterior parts possess the 

 greatest degree of elasticity, short of being 

 actually cloven, that can be imagined from the 

 sole being open to its centre and filled up with 

 the frog. In such a foot as the term Solid- 

 ungula would imply, or a continuous circle of 

 horn, no animal could long stand, much less 

 move, without great fatigue and pain from 



SB 2 



