102 ANATOMY OF VERTEBRATES. 



The ohdurator inter nus arises from the inner side of the oppo- 

 site margins of the pubis and ischium, where they form the 

 posterior boundary of the ohturatoy^ foramen, and from the corre- 

 sponding part of the obturator fascia ; the fleshy fibres converge 

 in a shghtly penniform manner to the strong round tendon which 

 glides through the notch, separated from the rest of the foramen 

 by a short, strong, transverse, unossified ligament, and is inserted 

 into the posterior part of the base of the trochanter. In its length 

 and size this muscle resembles the corresponding one in the 

 Ostrich and other Struthious birds. 



The gemellus is represented by a single small fleshy strip 

 arising from the margin of the obturator foramen, close to the 

 emer2:ence of the tendon of the obturator internus, with which it 

 is joined, and co -inserted into the femur. 



The quadratus is a broad fleshy muscle which arises from the 

 pubis, below the obturator foramen, and which increases in breadth 

 to be inserted into the femur internal and posterior to the obtu- 

 rator tendon. 



Abductor magnus} The largest and most remarkable of the 

 muscles which act upon the bones of the leg is that already 

 alluded to as the most superficial of those on the outer side of the 

 thigh. It has a broad, thin, triangular form, and arises from the 

 spines of the sacrum by a strong but short aponeurosis which 

 soon becomes fleshy ; the carneous fibres converge as they de- 

 scend," and pass into a thin aponeurosis at the lower third of the 

 thigh : this is closely attached to the muscles beneath {vastus 

 externus and crurcsus), then spreads over the outer and anterior 

 part of the knee-joint, is inserted into the patella, and into the 

 anterior process of the head of the tibia. 



Owing to the great antero-posterior extent of the origin of this 

 muscle, its anterior fibres are calculated to act as a flexor, its 

 posterior ones as an extensor, of the femur : all together combine 

 to abduct the thigh and extend the leg, unless when this is in a 

 state of extreme flexion, when a few of the posterior fibres glide 

 behind the centre of motion of the knee-joint. 



Sartorius.^ The origin of this muscle is characterised by an 



* xr. vol. iii. pi. 31, ii. 



* They are not divided into a superficial and deep layer, as in the Ostrich, but 

 forin a simple stratum, as in the Cassowary. Meckel regards the rectus femoris jis 

 entirely wanting in the Cassowary, supposing, with Cuvier, the present muscle to be 

 the analogue of the glutceus vmximus and tensor vagivte united. lie says that Profes- 

 sor Nitzsch observed a like absence of the rectus femoris in the Emeu. Cuvier calls 

 that muscle rectus anticus femoris, which is here described as the ^ pectineus.' 



^ X1-. vol. iii. pis. .31 and 3.5, i. 



