Fig. 82.—Diagram of a Horizontal Section of the Middle of the Forearm of the Left Leg of the Horse: Surface of the Inferior Segment of the Section.
1, Radius; 2, ulna; 3, posterior ulnar; 4, anterior ulnar; 5, great palmar (flexor carpi radialis); 6, flexors of the digits.
For this cause we do not find the square pronator in either the ox or the horse, but can demonstrate its presence in the dog and the cat.
It is very deeply situated. This is why, and also on account of the plan which we have traced for ourselves, we will simply say that it is situated on the postero-internal aspect of the skeleton of the forearm, and that it extends from the ulna to the radius.
It seems to us, however, sufficiently interesting to add that, instead of occupying, as in the human species, the inferior fourth of the two bones, it extends, particularly in the dog, over their whole length, with the exception of their superior and inferior extremities.
Muscles of the Hand
We will first recall that, in man, the palm of the hand is divided into three regions: a median palmar region, which is occupied by the tendons of the flexors of the digits, the lumbricales, and, deeply, by the interosseous muscles; an external region, or thenar eminence, formed by the muscles destined for the movements of the thumb; an internal region, or hypothenar eminence, which contains the muscles proper to the small digit and the palmar cutaneous muscle.
These muscles are found, more or less developed, in the dog and the cat.
In the ox and the horse we meet with no vestige of the muscles of the thenar or hypothenar eminences. Nevertheless, in these animals we find the muscles which belong to the central region of the palm. We refer to the lumbricales and the interosseous.
Although this fact has no relation to the object of our study, it appears to us interesting to announce that there are traces of the lumbricales found in the solipeds. These muscles are represented by two fleshy bundles, situated one on each side of the tendon of the deep flexor, above the ring of the tendon of the superficial flexor. These small muscles are continued as slender tendons, which become lost in the fibrous tissue of the spur, which is the horny process situated at the posterior part of the fetlock, and which is covered by the hairs, more or less abundant, which constitute the wisp.