Fig. 95.—Vertical Antero-posterior Section of the Foot of a Horse.
1, Third phalanx; 2, fibro-cartilage; 3, podophyllous tissue; 4, inferior part of the wall; 5, section of the wall of the hoof; 6, cutigerous cavity; 7, tendon of the anterior extensor of the phalanges; 8, reinforcing band coming from the suspensory ligament of the fetlock; 9, tendon of the superficial flexor of the phalanges; 10, tendon of the deep flexor of the phalanges.
In the interior of this horny box we find the third phalanx, a small sesamoid bone placed opposite to the posterior border of the latter, a portion of the inferior extremity of the second phalanx, and the tendons, which terminate at this region.
To the third phalanx are added two fibro-cartilaginous plates, flattened laterally, which prolong backwards the bone to which they are annexed. The inferior border of each of these fibro-cartilages is fixed by its anterior part to two osseous prominences situated at each of the angles which terminate the small phalanx behind; these prominences are: the basilar process and the retrorsal process ([Fig. 96]); by its posterior part, this border is continuous with a structure known as the plantar cushion (see [further on]).
The posterior border is directed obliquely upwards and forwards. The superior border, which is convex or rectilinear, is thin, and is separated from the posterior border by an obtuse angle. Finally, the anterior border, which is directed obliquely downwards and backwards, is united to the ligamentous apparatus, which keeps the second and third phalanges in contact.
These fibro-cartilages, at their upper extremities, project beyond the hoof, and therefore assist in the formation of the lateral regions of the foot,[35] at the part which is called the crown. They project less above the hoof in the posterior limbs.
[35] Here, for the first time, apropos of the hoof, we use the word ‘foot.’ As in osteology and in myology we have, for the sake of clearness of comparison, designated under this name the region limited above by the tarsus, it is necessary to point out here that we employ the same word for a more restricted region. This we did in conformity with the usage of veterinarians, who so designate the region of the hoof. It is necessary to explain this double employment of the word, and, further, to show the particular meaning ascribed to it.
