426 THE MUSCLES AND FASCIJE. 



and in front of the Gluteus maximus and short head of the Biceps, which separate 

 it from the Vastus externus. 



Nerves. The three Adductor muscles and the Gracilis are supplied by the 

 third and fourth lumbar nerves through the obturator nerve ; the Adductor mag- 

 nus receiving an additional branch from the sacral plexus through the great 

 sciatic. The Pectineus is supplied by the second, third, and fourth lumbar nerves 

 through the anterior crural, and by the accessory obturator, from the third lumbar, 

 when it exists. Occasionally it receives a branch from the obturator nerve. 1 



Actions. The Pectineus and three Adductors adduct the thigh powerfully : 

 they are especially used in horse exercise, the flanks of the horse being grasped 

 between the knees by the actions of these muscles. In consequence of the obliquity 

 of their insertion into the linea aspera they rotate the thigh outward, assisting 

 the external Rotators, and when the limb has been abducted they draw it inward, 

 carrying the thigh across that of the opposite side. The Pectineus and Adductor 

 brevis and longus assist the Psoas and Iliacus in flexing the thigh upon the pelvis. 

 In progression, also, all these muscles assist in drawing forward the hinder limb. 

 The Gracilis assists the Sartorius in flexing the leg and rotating it inward ; it is 

 also an adductor of the thigh. If the lower extremities are fixed, these muscles 

 may take their fixed point from below and act upon the pelvis, serving to maintain 

 the body in an erect posture, or, if their action is continued, to flex the pelvis 

 forward upon the femur. 



Surgical Anatomy. The Adductor longus is liable to be severely strained in those 

 who ride much on horseback, or its tendon to be ruptured by suddenly gripping the saddle. 

 And, occasionally, especially in cavalry soldiers, the tendon may become ossified, constituting the 

 "rider's bone." 



THE HIP. 



3. Gluteal Region. 



Gluteus maximus. Obturator internus. 



Gluteus medius. Gemellus superior. 



Gluteus minimus. Gemellus inferior. 



Pyriformis. Quadratus femoris. 



Obturator externus. 



Dissection (Fig. 255). The subject should be turned on its face, a block placed beneath 

 the pelvis to make the buttocks tense, and the limbs allowed to hang over the end of the table, 

 with the foot inverted and the thigh abducted. Make an incision through the integument along 

 the crest of the ilium to the middle of the sacrum, and thence downward to the tip of the coccyx, 

 and carry a second incision from that point obliquely downward and outward to the outer side 

 of the thigh, four inches below the great trochanter. The portion of integument included 

 between these incisions is to be removed in the direction shown in the figure. 



The Gluteus maximus (Fig. 256), the most superficial muscle in the gluteal 

 region, is a very broad and thick, fleshy mass of a quadrilateral shape, which 

 forms the prominence of the nates. Its large size is one of the most characteristic 

 points in the muscular system in man, connected as it is with the power he has of 

 maintaining the trunk in the erect posture. In structure the muscle is remarkably 

 coarse, being made up of muscular fasciculi lying parallel with one another, and 

 collected together into large bundles, separated by deep cellular intervals. It 

 arises from the superior curved line of the ilium and the portion of bone, including 

 the crest, immediately above and behind it ; from the posterior surface of the lower 

 part of the sacrum, the side of the coccyx, the aponeurosis of the Erector spinae 

 muscle, the great sacro-sciatic ligament, and the fascia covering the Gluteus medius. 

 The fibres are directed obliquely downward and outward; those forming the upper 

 and larger portion of the muscle, together with the superficial fibres of the lower 



1 Professor Paterson describes the Pectineus as consisting of two incompletely separated strata, of 

 which the outer or dorsal stratum, which is constant, is supplied by the anterior crural nerve, or in 

 its absence by the accessory obturator, with which it is intimately related; while the inner or ven- 

 tral stratum, when present, is supplied by the obturator nerve. Journal of Anatomy and Physiology, 

 vol. xxvi., p. 43. 



