430 PLANTAR SYSTEM. 



diameter of the ground-surface of the hoof, terminating a Uttle 

 beyond the central point (or what would be the central point) of 

 the sole — or rather shooting directly through it, so as to anni- 

 liilatethe spot. Posteriorly, it is embraced by the heels of the 

 wall ; laterally, it possesses firm and solid junctions with the 

 bars, and through their medium with the sole: and these unions 

 are etFected not by simple apposition and cohesion of surface, 

 but by a lameUated structure, apparent on the sides both of the 

 frog and bars, by which the parts are reciprocally dovetailed 

 into each oiher. Lamella) are discoverable upon its sides, even all 

 round the toe of the frog ; and this is a circumstance that con- 

 firms me in my belief that the bars reach thus far. 



Figure. — The frog may be called pyramidal, or cuneiform, or 

 triangular in figure ; its outline forming the geometrical figure 

 denominated an isosceles triangle. I know of no comparison so 

 familiarly apt as that of resembling it to a ploughshare : not only 

 do they both correspond, as near as such comparisons can be 

 expected to do, in outline and make, but they likewise exhibit 

 a singular coincidence in function ; the frog, like the plough- 

 share, being intended by its point to plough or divide the surface 

 of the earth, and in that manner serve as a stay or stop to the 

 foot. 



Division. —We distinguish in the frog two surfaces, an inferior 

 and a superior ; two sides ; a point or toe ; and two bulbs or 

 heels. 



SURFACES. — Both surfaces of the fro^ manifest striking- 

 irregularities, and these are respectively reversed, making one 

 surface the exact counterpart of the other. In other respects, 

 the only difference they exhibit, is, that the superior exceeds the 

 inferior both in length and breadth. 



The Inferior Surface presents to our view a remarkable 

 cavity, broad, deep, and triangular in its shape, bounded on 

 the sides by two sloping prominences, which divaricate from the 

 convexity forming the toe of the frog, and terminate, after a 

 short divergent course, at the heels. This cavity or hollow is 

 denominated 



The Cleft of the Frog : with seeming reference to the re- 

 lationship existing, through its presence, between the horse's 

 foot and the cloven one of the ox, deer, sheep, &c. In conse- 

 quence of its sides sloping inward, the cleft at bottom gapes 

 wide open ; but along the top is roofed by a simple linear mark 

 running from before backward. The horn is kept continually 

 soft and pliant within the cleft by a peculiar secretion from the 

 sensitive parts its covers, the odour of which is notorious. 



The solid wedge-like portion of horn in front of the cleft, ex- 

 tending from it to the point of the toe, has been observed by 



