112 



OF THE MUSCLES. 



vertebrae. Insertion. Into the tubercle on the brim of the 

 pelvis. 



Psoas magnus. Origin. From the angles of the last 

 three ribs ; and from the transverse processes of the lumbar 

 vertebrae. Insertion. By a tendon, which is common also 

 to the next muscle, into the internal trochanter of the femur. 



Iliacus {Fig 7. I). Bifid superiorly. Origin. By the 

 larger head: from the anterior spinous process, and the 

 venter of the ilium. By the small head : which lies between 

 the two psoas muscles ; from the venter of the ilium. In- 

 sertion. By tendon, common also to the psoas magnus, 

 from which the iliacus cannot be fairly separated ; into the 

 internal trochanter of the femur. Action of the three heads. 

 To roach the lumbar vertebrae; and in galloping, con- 

 jointly with the abdominal muscles, to draw the pelvis 

 forward ; and to place the hind leg well under the body 

 during violent motion. The three are also in use in 

 more moderate action ; but then their power is less 

 marked. They are likewise of great service during copu- 

 lation. 



Gluteus internus {Plate III. 9). Origin. From the 

 sacro sciatic ligament ; and the roughened elevation above 

 the acetabulum. Insertion. Into the inferior tubercle of the 

 great trochanter ; and into the capsular ligament of the hip 

 joint. Action. To protect the capsular ligament; and to 

 keep close the head of the femur. 



Obturator externus {Fig 7.5). Origin. From the 

 brim of the obturator foramen ; from the membrane cover- 

 ing the opening ; and a small portion also from the tendon 

 common to the gracihs and abdominal muscles. Insertion. 

 Into the sulcus behind the great trochanter ; and into the 

 ridge extending from it by tendon. Action. To flex the 

 femur. 



Pyriformis. Origin. From the first transverse process 

 of the sacrum ; and the venter of the ilium. Insertion. The 

 tendon of the muscle leaves the pelvis, and winds over a 

 synovial groove upon the border of the innominata. Having 

 gained the exterior of the pelvis the tendon is joined by that 

 of the obturator internus ; and into this common tendon are 

 inserted some of the fibres of the gemini. The tendon is 



