Fig. 8.—The frog band detached from wall by a small wedge.
The point of the frog, much the harder part, extends forward to the centre of the sole. Though situated between the bars the frog is only attached to their upper border—the sides remaining free and separate. Thus on each side is formed a deep fissure which permits the frog to expand laterally when compressed, without such force being continued to the sides of the foot. The frog is elastic, and when pressed upon must expand slightly. If these spaces between frog and bars did not exist, the foot would be injured when the frog was compressed by the weight of the horse—either the sensitive parts within would be bruised or the heels would be forced apart.
The centre of the frog presents a depression or "cleft" caused by the doubling in of the horn. Few shod feet exhibit it of natural appearance, and the term cleft, by implying a narrow deep fissure, keeps up the false notion. The cleft should be shallow and rounded. It serves two purposes—it increases the mobility of the frog, and by breaking the regularity of surface affords a secure foot-hold on level ground.
The prominence of the frog might lead a superficial observer to consider it a thick solid mass; and I believe this mistake is the cause of its too frequent mutilation. It is merely a layer of horn following the outline of the structures within, which are similarly prominent and irregular in surface. ([Figs. 9] and [10]). The diagrams show a section through the point and through the cleft of the frog.
Fig. 9.—Section of Foot at cleft.