FASCIA AND MUSCLES OF THE PELVIC LIMB 273 



METACARPAL MUSCLES 



The five muscles of this group are either reduced to vestiges or modified greatly 

 in structure. 



1, 2. Lumbricales (internus et externus). — These are two small muscles which 

 lie on either side of the flexor tendons above the fetlock. They arise from the 

 deep flexor tendon, and are lost in the fibrous tissue which lies under the nodule of 

 horn or ergot at the fetlock (Fig. 447). Their action is inappreciable. The size 

 of these muscles is subject to much variation. Often very little muscular tissue 

 can be found, but the small tendon is constantly present. 



Blood-supply. — Metacarpal arteries. 



Nerve-supply. — Median and ulnar nerves. 



3, 4, 5. Interossei. — These are three in number in the horse, and are situated 

 chiefly in the metacarpal groove. Tw^o, the internus and externus, are very small 

 muscles, each of which arises from the corresponding small metacarpal bone near 

 its proximal extremit^^ and is provided with a delicate tendon which is usually lost 

 in the fascia at the fetlock (Fig. 150). They have no appreciable action. Their 

 blood- and nerve-supply is the same as that of the preceding muscles. 



The interosseus medius is so much modified that it is usually termed the 

 suspensory, or superior sesamoidean ligament. It contains little muscular tissue, 

 being transformed very largely into a strong tendinous band, bifurcate below% and 

 having for its chief function the supporting of the fetlock. It has been described, 

 in deference to common usage, with the ligaments. 



fasci.e and muscles of the pelvic limb 



The Fascia 



« 



The iliac fascia (Fascia iliaca) covers the ventral surface of the iliacus and psoas 

 muscles, over which it is tightly stretched (Fig. 450). It is attached internally to 

 the tendon of the psoas minor, externally to the inguinal (Poupart's) ligament 

 and the external angle of the ilium. Its anterior part is thin. Posteriorly, it is 

 in part attached to the ilium, in part becomes continuous with the pelvic fascia. 

 It furnishes surfaces of origin for the sartorius, cremaster externus, and transversus 

 abdominis muscles. 



The pelvic fascia (Fascia pelvis) lines the cavity (parietal layer) and is reflected 

 on the viscera at the ])elvic outlet (visceral layer). LaminiE are detached from it 

 to strengthen the various peritoneal folds. 



The superficial fascia of the gluteal region is continuous with the aponeurosis 

 of the panniculus. It covers and partly blends with the deep fascia. The gluteal 

 fascia (Fascia glutea) covers the superficial muscles of the region, and detaches 

 intermuscular septa, which pass between the muscles. It is attached to the sacral 

 spines, the dorsal sacro-iliac ligament, and the angles of the ilium, and is continuous 

 in front with the lumbo-dorsal fascia, behind with the coccygeal fascia. Its deep 

 face gives origin to fibers of the superficial and middle glutei, the biceps femoris, 

 and the semitendinosus, so that care is necessary in dissecting it ofT these muscles. 

 The chief intermuscular septa are: (1) One which passes between the superficial 

 gluteus and the biceps femoris; (2) one between the biceps and semitendinosus, 

 from which a lamella is detached which passes between the middle and posterior 

 portions of the biceps and is attached to the tuber ischii; (3) one between the 

 semitendinosus and semimembranosus, which is attached to the sacro-sciatic liga- 

 ment and tuber ischii; it furnishes origin for fibers of the long head of the semi- 

 membranosus. 



The fascia lata is continuous with the preceding, and covers the muscles on the 

 18 



