288 THE MUSCLES. 



when its fixed point is above ; when the leg is fixed, it becomes one of the 

 active agents in rearing 



3. Semimembranosus. (Figs. 129, 10 ; 130, 13.) 

 Synonyms. Ischio-tibialis interims Girard. (Great ischio-femoralis LeyJi.) 



Situation Volume Extent Direction. Situated within the semiten- 

 dinosus, and shorter and thinner than it, the Semimembranosus extends from 

 the ischium to the inferior extremity of the femur, and follows an oblique 

 direction downwards and forwards. 



Form Structure. Elongated vertically, depressed on each side, pris- 

 matic, thick at its anterior, and very thin at its posterior borders. It is also 

 voluminous at its upper extremity, which has a small prolongation whose 

 point ascends to the base of the tail ; contracted, and terminated by a short 

 tendon at its inferior extremity. It is formed of thick muscular fasciculi, 

 which all terminate, below, on the tendon. 



Attachments. Above : 1, To the aponeurosis of the coccygeal muscles, 

 by the thin prolongation from its superior extremity ; 2, To the ischiatic 

 tuberosity, and on the inferior face of the ischium. Below, to the small 

 eminence situated within the internal condyle of the femur. 



Relations. Inwards, with a very thin prolongation from the gluteal 

 aponeurosis, and with the ischio-cavernous muscle and short adductor of the 

 leg; outwards, with the semitendinosus, the long vastus, and the sciatic 

 nerves ; in front,, with the great adductor of the thigh, which is so intimately 

 united to it that some difficulty is experienced in separating their fibres. 



Action. It is an adductor of the limb and an extensor of the thigh, when 

 its fixed point is above ; but when the femur is fixed, it is an auxiliary in 

 rearing. 



C. Internal Crural Region. 



This region comprises nine muscles, applied in three superposed layers 

 against the inner aspect of the thigh. These are : the long and short ad- 

 ductor of the leg, forming the superficial layer ; the pectineus and the small 

 and great adductors of the thigh, forming the middle layer. Those of the 

 deep layer that is, the square crureus, external obturator, internal obturator, 

 and gemini of the pelvis, are not all situated on the inner face of the femur, 

 one of them being contained within the pelvic cavity. With these muscles, 

 which do not present a very considerable volume, another region might be 

 formed and designated the deep pelvi-crural, or coxo-femoral region. 



Preparation. 1. Place the subject in the first position. 2. Prepare on one side the 

 two muscles of the superficial layer, by removing the slight fibrous layer covering them, 

 the internal crural aponeurosis, and the inferior parietes of the abdomen. 3. To expose, 

 on the opposite side, the three muscles of the middle layer, cut through the two 

 adductors of the leg, and turn them back to the right and left; separate the semi- 

 membranosus from the great adductor of the thigh ; it may be even useful, in order to 

 study the latter muscle, to remove the entire mass of the three ischio-tibial muscles. 

 4. Dissect the small deep muscles on a separate piece, as shown in figures 90 and 131. 



1. Long Adductor of the Leg. (Fig. 130, 8.) 



Synonyms. Sublumbo-tibialis Girard. (Sartorius Percivall Internal ilio-rotu- 

 leus Leyh.) 



Form Situation Direction. This muscle is long, thin, and flattened, 

 narrow at its inferior extremity, and situated at first within the abdominal 



