162 COUES, 



Three ischio-femoral muscles remain to be described; their de- 

 termination may be attended with difficulty. One ( a, see below) is 

 pretty obviously obturator externus; another (6) appears like a par- 

 tial segregation from a ; the third (c) should represent obturator in- 

 ternus, although it is cut off from the inner surface of the ischium, has 

 no radiation of tendon, and is unaccompanied by gemelli. All three 

 proceed to the back part of the femur, at the expanded intertrochan- 

 teric surface, instead of conniving at a "digital fossa." 



a. With broad rounded origin from the whole outer surface of 

 the ischium and obturator membrane, narrowing as it passes straight 

 outward and forward across the back of the hip-joint to definite inser- 

 tion (see above) between the insertions of b and c. 



b. Like a part of the preceding, and somewhat blended therewith, 

 but mainly distinct. It arises fleshy from the base of the ischio-pubic 

 ramus along and below the articulation of the marsupial bones, and 

 from the upper margin of the obturator foramen ; passes back of the 

 hip-joint and entotrochanter to a broad, fleshy insertion into most of 

 the expanded intertrochanteric space. This and a extend and evert 

 the femur. 



c. Arises fleshy from the whole of the thickened concave posterior 

 border of the ischio-iliac ramus, from tuber ischii to acetabulum ; 

 passes outward and forward across the back of the hip-joint to the 

 ectotrochanter, where it is inserted fleshy into the border and back 

 surface of that process just below its apex. Its action is similar to 

 those of the two preceding. 



In examining the operations of the muscles that collectively act 

 upon the femur, there is probably not much to note, after we have 

 seen the permanent abduction and eversion of the thigh. The gen- 

 eral preponderance of extensors over flexors, etc., is in relation to 

 the force of the backward stroke in swimming. The more interest- 

 ing features of the hind limb are shown mainly from the knee down- 

 ward. 



b. Acting upon the leg. 



The most remarkable thing about the crural muscles is the pres- 

 ence of the intertibialis (a feature unique in mammalian myology?). 

 Probably the next most so, is the entrance of the enormous ecto-glu- 

 tceus into the crural instead of the femoral group, its low insertion at 

 the foot, and its connection there with a caudo-tibial extensor. Al- 

 though the latter muscle occurs among marsupials, here we have it 

 under special conditions. The gracilis is second only to the great 

 glutseus in bulk, and sends a peculiar slip backward to the cloaca- 

 The biceps is large and though rather unusually thin and fan-shaped, 

 is exhibited in the normal condition of that muscle ; that is, with only 

 one (anischial) head, and no femoral attachment its bicipital dis- 



