As for the interosseous muscles, they are represented by the suspensory ligament of the fetlock, and by two other small muscles, tendinous throughout, which are situated between the principal metacarpal and the rudimentary ones.
The suspensory ligament of the fetlock is considered an interosseous muscle, on account of the red fleshy striations which it contains, and from certain relations which it forms with the tendon of the common extensor of the digits or anterior extensor of the phalanges. This ligament ([Fig. 75], 26; [Fig. 77], 13), which plays an important part in the standing position as a support of the foot, is a fibrous band situated between the tendons of the flexors of the digits and the principal metacarpal. It arises above, from the second row of the carpals, descends towards the fetlock, where it divides into two branches, which are inserted into the large sesamoid bones. At the same level, this ligament gives off two fibrous bands which, passing downwards and forwards, join the tendon of the anterior extensor of the phalanges, blending with it, after having each crossed one of the lateral aspects of the pastern. We have already referred to these bands ([p. 183]).
It is with these latter that are blended the long and slender tendons which form in a great measure the two other interosseous muscles previously described.
A ligament of the same kind is found in the ox ([Fig. 74], 23).
MUSCLES OF THE POSTERIOR LIMBS
Muscles of the Pelvis
The muscles which specially interest us in this region, because of their superficial position, are the gluteus maximus and the gluteus medius. As for the gluteus minimus, it is deeply situated, and more or less sharply marked off from the second of the preceding muscles.
Inasmuch as the gluteus medius is more simple in arrangement than the maximus, and will aid us in arranging our ideas in connection with the latter, it is with the study of it that we will commence.
Gluteus Medius ([Fig. 68], 29; [Fig. 69], 26; [Fig. 70], 35).—This muscle, as in man, occupies the external iliac fossa. But this latter being directed differently in the digitigrades and the ungulates, as we have pointed out in the section on osteology (see [pp. 91] and [99]), the muscle in question has consequently not the same direction in the two groups of animals, being turned outwards in the first, and upwards in the second.
It is the thickest of the glutei, and gives to the region which it occupies a rounded form.