324 FASCLH AND MUSCLES OF THE HORSE 
Relations.—Laterally, the skin and fascia, the biceps, and the medial head 
of the gastrocnemius; medially, the coccygeal fascia, the sacro-sciatic ligament, 
the semimembranosus; anteriorly, the biceps femoris, branches of the femoral 
artery, and the great sciatic nerve. 
Blood-supply.— Posterior gluteal, obturator, and posterior femoral arteries. 
Nerve supply.— Posterior gluteal and great sciatic nerves. 
Origin of obliquus ab- 
dominis internus 
Inguinal ligament (part 
removed ) 
Iliacus 
Tensor facia late 
Rectus femoris — 
Vastus medialis 
Sartorius 
Gracilis — 
Patella —— 
X 
Medial patellar ligament \ 
Tendon of sartorius ———T 
ie 
Tendon of gracilis —* 
y 
* : ; . 
Fascia cruris ; mR Ba 
Fic. 287.—Muscies or PeEtvis AND THIGH OF YouNG Horse, Ricur Stpe; Meptau View. 
1, Psoas minor, and 1’, its insertion; 2, psoas major; 3, 3’, heads of obturator internus; 4, sacro-coceygeus ven~ 
tralis; 5, coceygeus; 6, retractor ani (cut); 7, sacro-sciatic ligament; 8, lesser sciatic foramen; 9, semimembranosus; 
10, lumbo-sacral plexus; 11, obturator nerve and vessels (cut); 12, femoral vessels (origin); 13, pubis; 14, prepubic 
tendon; 15, deep inguinal lymph glands; 16, opening for external pudic vein. Vertebra# are numbered by regions. } 
7. Semimembranosus! (Figs. 276, 287, 288, 576).—This very large, three- 
sided muscle lies on the medial surface of the preceding muscle and the gastroc- | 
nemius, and has two heads of origin. 
Origin.—(1) The posterior border of the sacro-sciatic ligament; (2) the ventral 
surface of the tuber ischi. 
1 This muscle was incorrectly designated the adductor magnus by Percivall and Strange- 
ways. Its name, however, is not at all descriptive of its structure in the domesticated animals. 
