274 FASCIA AND MUSCLES OF THE HORSE 



outer surface and front of the thigh. It is tendinous and very strong, 'and for the 

 most part easily separable from the underlying muscles. It furnishes insertion to 

 the tensor fascige latse and to the biceps femoris (in part), by both of which it is 

 tensed. At the stifle it is attached to the patella and the inner and outer straight 

 ligaments. Internally it is continuous with the internal femoral fascia. It fur- 

 nishes the following intermuscular septa: (1) One which passes between the vastus 

 externus and biceps femoris to be attached to the external trochanter of the femur; 

 (2) two which pass between the three branches of the biceps femoris; (3) a fourth 

 between the biceps femoris and semitendinosus. 



The internal femoral fascia (Fascia femoralis medialis) covers the superficial 

 muscles on the inner surface of the thigh. At its up])er part it is joined by part of 

 the aponeurosis of the external oblique muscle (Lamina femoralis) (Fig. 450). The 

 posterior part is thin. It is continuous with the fascia lata in front and the crural 

 fascia below. At the stifle it fuses with the tendons of the sartorius and gracilis. 



The crural fascia, or fascia of the leg (Fascia cruris), consists of three layers. 

 Two of these invest the entire region and may, therefore, be termed the common 

 fasciae. The superficial layer is a continuation of the fascise of the thigh, while the 

 second layer may be regarded chiefly as a continuation of the tendons of the super- 

 ficial muscles of the hip and thigh (biceps femoris, semitendinosus, tensor fasciae lata^, 

 sartorius, and gracilis). The two layers frequently fuse, and are attached chiefly 

 to the patellar ligaments and the crest and internal surface of the tibia. About 

 the middle of the leg the two layers unite behind the deep flexor of the digit and 

 form a strong band which passes downward in front of the tendons of the gastroc- 

 nemius and superficial flexor, to be attached with the latter to the anterior and 

 inner part of the tuber calcis. This may be regarded as an accessory or tarsal 

 tendon of insertion of the biceps femoris and semitendinosus. The third layer 

 forms sheaths for the muscles, furnishing origin in part to their fibers. Two im- 

 portant intermuscular septa are detached, viz.: (1) One which passes between the 

 anterior and lateral digital extensors to be attached to the fibula and the external 

 border of the tibia; (2) one between the lateral extensor and the deep flexor. 



The tarsal fascia (Fascia tarsi) fuses with the ligaments and bony prominences 

 of the region. It is strong and tendinous in front, and joins the tendon of the an- 

 terior extensor below the joint. Laterally, it is thin and fuses with the ligaments. 

 Posteriorly, it is very thick and strong, forming an annular ligament which stretches 

 from the internal lateral ligament to the fibular tarsal bone and the plantar liga- 

 ment. This converts the groove at the back of the hock into a canal, in which 

 arc the deep flexor tendon with its synovial sheath and the plantar ner\'es. In 

 front of the tarsus and above and below it there are three aimular ligaments 

 (Ligamenta transversa). The proximal one binds down the tendons of the anterior 

 extensor, peroneus tertius, and tibialis anterior on the distal end of the tibia. The 

 middle one stretches from the fibular tarsal bone to the outer tendon of the pero- 

 neus tertius, forming a loop around the tendon of the anterior extensor. The distal 

 band stretches across the proximal extremity of the large metatarsal bone and in- 

 closes the tendons (and sheaths) of the two extensors of the digit. 



The metatarsal and digital fasciae do not differ materially from those of the 

 correspoutUng regions of tlie thoracic linil). 



The Muscles 



I. THE SUBLUMBAR MUSCLES (Figs. 450, 456) 

 The muscles of this group are not confined to the sublumbar region, but ex- 

 tend beyond it both before and behind. Their chief function is to flex the hip 

 joint. Two, however, — the psoas minor and the quadratus lumborum, — have 

 not this action. 



