PLATE XXI. 

 DEEP VIEW OF THE FRONT OF THE THIGH. 



In this plato a dissection of the deeper parts of Scarpa's triangle and front of thigh 

 is shown. The adductor longus has been cut and the middle part removed ; the 

 pectineus has also been divided and the ends turned back, exposing the obturator 

 externus and its fascia and the obturator nerve. The rectus muscle has also been 

 divided : this muscle has two heads of origin from the ilium, a straight head arising 

 from the inferior spinous process and a reflected head arising just above the acetabulum : 

 the latter is the original head of origin in early foetal life, the straight head being a 

 later development, appearing about the third month as a thickening in its sheath. This 

 double origin allows the muscle to act forcibly as an extensor in the different positions 

 of the limb, for in the extended position the straight head will give the point d'appui, 

 while the reflected will act best in the flexed position of the limb. Professor Cleland 

 states that the presence of the straight head of the rectus probably saves that muscle at 

 least half an inch more contractile muscular substance, and is thus an economy to the 

 body. The deep prolongation of the fascia lata beneath the tensor vaginas femoris is 

 also well shown : it is usually a well-marked and powerful band, and is attached above 

 to the ilium, just below the origin of the tensor. The profunda femoris is usually 

 dr-;cril)ed as having four perforating branches, one given off above the level of the 

 adductor brevis and piercing the magnus to get to the back of the leg, another piercing 

 both these muscles, and two given off below the level of the brevis and piercing the 

 magnus alone. Very often, however, the first and second are conjoined, and pierce the 

 brevis and magnus ; sometimes there are two branches, and then it is usually the rule 

 for them both to pierce the brevis as well as the magnus. 



Ni i i. / of Pectineus. The pectineus of man is usually considered to be a 



dorsal muscle, and as such would be supplied by a dorsal nerve the anterior crural. 

 In about 8 per cent, of cases it also gets a branch from the obturator ; when this 

 happens it is probably because the muscle then consists of two separate elements : a 

 dorsal one supplied by the anterior crural, a dorsal nerve, and the other a ventral by the 

 obturator, a ventral nerve. In the horse it consists of two layers, a superficial, supplied 

 by the anterior crural and resembling the pectineus of man, and a deep layer supplied 

 by the obturator and seeming to belong to the adductors, the two being separated by the 

 pubo-femoral ligament. In reptiles this double nerve supply is frequently seen. The 

 muscle is occasionally divided into two parts in man. The accessory obturator nerve 

 which sometimes supplies it would be better named accessory anterior crural, because 

 (1) its origin is more closely allied to the anterior crural than obturator; (2) if it runs 

 with obturator it courses over the pubic ramus ; (3) it supplies a portion of the pectineus 

 in place, of the anterior crural. 1 



Mr. Sutton ' 2 thinks that the ligamentum teres of the hip joint is the lost tendon 

 of the pectineus muscle, for he finds that (1) in the lizard (Sphenodon) the tendon of 

 the ambiens (pectineus) passes inside the capsule to the head of the femur ; (2) in the 

 ostrich (Struthio Camelus) the ligament is continuous with the ambiens across the 

 cotyloid cavity by means of fibrous tissue ; (3) in the horse (Equus) the ligamentum 

 teres is in two parts, one be^ng hidden within the joint, the cotyloid portion, and one 

 being attached to the pubes, the pubo-femoral portion from this band the pectineus 

 partly arises ; (4) in man the ligamentum teres is a fibrous band carrying blood vessels 

 to the head of the femur. 



1 Dr. Patterson, Journ. of Anat. and Phys. vol. xivi. 

 1 Sutton, Ligaments Nature and Morphology, p. C9. 



