FASCIA AND MUSCLES OF THE PELVIC LIMB THE FASCIA 317 



Nerve-supply. — Median and ulnar nerves. 



The five muscles of the metacarpus and digit are either reduced to vestiges or 

 modified greatly in structure. 



1, 2. Ltunbricales (medialis et lateralis). — These are two very slender fusiform 

 muscles which he on either side of the flexor tendons above the fetlock. They arise 

 from the deep flexor tendon, and end in the fibrous tissue which lies under the nod- 

 ule of horn at the fetlock which is known as the ergot (Fig. 572). 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. Two, the medialis and lateralis, are very small 

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

 its proximal extremity, and is provided with a delicate tendon which is usually lost 

 in the fascia at the fetlock (Fig. 240). 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 (Tendo interosseus), 

 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. 



Fascls: and Muscles of the Pelvic Limb 

 The Fascia 



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

 muscles, over which it is tightly stretched (Fig. 575). It is attached medially to 

 the tendon of the psoas minor; laterally it is attached to the tuber coxae and blends 

 with the deep layer of the limibo-dorsal fascia. Its anterior part is thin. Pos- 

 teriorly it is continuous with the inguinal ligament and the pelvic fascia. It fur- 

 nishes surfaces of origin for the sartorius, cremaster externus, and transversus ab- 

 dominis muscles. 



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

 at the pelvic outlet is reflected on the viscera to form the visceral layer. Laminae 

 are detached from it to strengthen the various peritoneal folds. 



The superficial fascia of the gluteal region is thin and is closely adherent to 

 the deep fascia. A subcutaneous bursa may be found on the tuber coxae. The 

 gluteal fascia (Fascia glutea) covers the superficial muscles of the region, and de- 

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

 sacral spines, the dorsal sacro-iliac ligament, and the tubera of the ilium, and is con- 

 tinuous 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 off 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 semi- 

 tendinosus, from which a lamella is detached which passes between the middle and 

 posterior parts 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 superficial fascia of the thigh presents no exceptional features, but the deep 



