The other muscles inserted into the great trochanter — namely, the glutceus n7inimus, the quadratus fenzoris, the obturator externus, the obturator internzis, the gemelli, and the Ara midalis —present in all quadrupeds a disposi tion similar to that which they have in the human body.
The muscles passing between the pelvis and the lesser trochanter, and also those that arise from the pubis to be implanted into the in ternal surface of the thigh, in the generality of quadrupeds, correspond very accurately with those of man. In the horse these are the psoas magnus, the iliacus, the pectinceus, and the triple adductor, none of which offer any peculiarity worthy of remark.
The flexor muscles of the leg are the biceps flexor cruris, the senzimembranosus, the senzi tendinosus, the sartorius, the gracilis, and the poplitceus, all of which are enclosed by the dense fascia of the thigh, or fascia lata, which is kept tense by the action of' a special muscle named the tensor vagina, femoris.
The last-named muscle, called also the museulus fascice latce (ileo-fascien) arises in the horse from the anterior portion of the crest of the ileum, whence it descends obliquely downwards, enclosed between two layers of the fascia, covering the thigh, into wh ch it is strongly inserted.
,The extensor muscles of the thigh— v7z. the biceps (ileo-rotulien), the vastus internus, the vastus externus, and the cruralis — offer in all quadrupeds the same general disposition as in man, the three last forming one great common muscle (triftmoro-rotulien). The anterior mar gin of the thigh in the horse and in other quadrupeds is fortned by the sartorius (ileo pretibien), which here, from its position and office, has been named by hippotomists the " long adductor of the thigh." The biceps (ischio-peronien) in the horse and the greater number of quadrupeds, not even excepting the quadrumana, arises by a single origin, which is derived from the ischium, and the neighbouring ligaments and fascial expan sions. This muscle covers a large proportion of the outer surface of the thi,di : its principal insertion is into the head of the fibula, but it likewise throughout its whole length contracts extensive and important attachments with the fascia lata, so that it also becomes a powerful extensor of the thigh. There is moreover, in the horse and in the Ruminantia, a distinct portion of the biceps derived from the sacro sciatic aponeurosis, the fibres of which are directed obliquely from before backwards, which, meeting the ischiatic portion at an angle, form with it a kind of raphe, which is prolonged for some distance. This muscle is
called by Bourgelat the " easing longus" of the thigh.
The gracilis (pubio-pretibien) is in all quad rupeds avery considerable muscle, more especi ally in such as have the thigh much shortened, as is the case in the horse, and the ungulata generally. It is called by Bourgelat the " short adductor of the thigh," whilst he gives the name " gracilis" to the semitendinosus.
The semimembranosus (ischio-sous-tibien) and the senzitendinosus (ischio-pretibien) have in all quadrupeds the same origin and general ar rangement as in man ; but both of them are in the lower animals inserted into the tibia by a broad aponeurosis. It must also be remarked that their insertion extends much lower down than in the human subject, a circumstance which causes the leg to be permanently kept in a semiflexed condition ; and is one of the great obstacles to their walking in an upright position. Even in the Quadrumana these muscles have their insertions very low down in the leg.
The poplitceus has nothing remarkable in its disposition.
Muscles implanted into the foot. The gas trocnemii (bi-fernoro-calcanien) and the solccus (tibio-calcanien) are less considerable muscles, as regards their comparative size in quadru peds, than in the human race : nevertheless their general disposition is invariably the same as in man. In the Solipeda, the solous is remarkably slender and feeble.
The plantaris (femori-calcanien). — In the Solipeds this muscle is remarkably developed, so much so indeed as apparently to repre sent the flexor sublimis. In the horse this muscle arises under the external head of the gemellus from a large fossa in the os fe moris above the external condyle : its tendon is continued downwards, and runs over the extremity of the os caleis, where it is en closed in a sheath formed by strong liga rnents, which prevent it from slipping out of its place; passing on from this point, it di vides, to be inserted upon each side of the posterior surface of the great pastern bone towards its inferior extremity, here giving passage between its two insertions to the ten don of the long flexor of the toe, which it serves to bend down closely to the pastern when the fetlock joint is bent, thus seeming to perform the functions both of the plantaris and of the short flexor of the toes.