S7 



The biceps and se- 

 mimembranosus act in 

 planes parallel to the 

 plane of motion of the 

 knee joint, and from 

 their mode of action 

 must both have result- 

 ants passing through 

 the junction of the 

 thigh and leg, so that 

 they must be regarded 

 as principally exten- 

 sors of the thigh, and 

 not as flexors of the 

 leg. The semitendino- 

 sus, on the other hand, 

 acts as a flexor of the 

 leg, and seems to ab- 

 duct by the same angle 

 that gracilis adducts; 

 so that, considering 

 that their weights are 

 nearly equal, the re- 

 sultant of gracilis and 

 semitendinosus will 

 also lie in the plane of 

 motion of the knee 

 joint. 



6. JK. gracilis weighs 



9oz. 



7. M. * adductor 

 magnus weighs 27 J oz. 



Origin, inner border 

 of symphysis pubis, and 

 round the edge of the 

 M. obturator externus, 

 as far as the tuber 

 ischii. 



Insertion, along the 

 linea aspera, through 

 entire length of the 

 back of the femur. 



8. M. adductor Ion- 

 gus weighs . . 2f oz. 



Fig. 14. 



LEFT LEG OF LION. 



(with biceps fernoris reflected, to show the deeper muscles). 



A, 31. biceps fernoris, reflected. 



B, 31. glutceus maximus. 



c, 31. agitator caudw. 



d, 31. glutams medius, its lower border reflected, to show, 



e, 31. gluteus minimus. 



f, s, M. vastus externus. 



G, 31. semitendinosus. 



H, M. semimembranosus. 

 k, 31. bicipiti accessorius. 

 ij, Tuber ischii. 



M, 31. gastrocnemius. 



n, Portion of gastrocnemius, sending a separate tendon to 



the patella, 



o, Lateral ligament of knee, 



p, Patella. 



q, 31. iliocapsularis. 



e, 31. rectus fernoris. 



* The action of the adductor magnus is one of the most complicated in animal mecha- 

 nics — for its origin is a curve, and its insertion a line, and these lie in different planes. 

 Probably, in the Lion, half its muscular force is expended in simple extension of the 

 femur, and the remaining portion, as in man, opposes the glutceus medius. 



