53 



Its action is to the outside of the plane that coincides with the greatest 

 diameter of the highly elliptical cross section of the femur. 



M. v. e. 2. Arises from the whole outer surface of the femur (Fig. 7) ; 

 it has an insertion similar to that of M. v. e. 1 ; its weight is . . . 5 oz. 



9, 10. M. vastus internus, like the preceding, is composed of two 

 parts, whose origins are shown in Fig. 8 — 



M. v. i. 1 . Arises from the upper and inner 

 surface of the femur, and is inserted into the 

 inner side of the head of the tibia, into the inner 

 edge of the patella and of the ligamentum pa- 

 tellae ; its weight is 13-Joz. 



M. v. i. 2. Arises from the lower portion of 

 the inner surface of the femur, and is inserted 

 into the tendon of the former (M. v. i. 1); its 

 weight is 3 J oz. 



The resultant plane of these two muscles 

 lies as much to the inside of the plane of maxi- 

 mum strength of the femur, as that of the vasti 

 externi lies to the outer side of the same plane. 



11. 31. crurceas. — Its origin, which lies al- 

 together on the inner side of the femur, is 

 shown in Fig. 8 ; it is inserted without a ten- 

 don into the patella ; its weight is . . . oz. 



Its plane of moment coincides very nearly 

 with that of the vasti interni, just described ; 

 and it is almost impossible to avoid coming to 

 the conclusion, that the peculiar elliptical cross 

 section of the femur, and its longitudinal plane 

 of maximum strength, are contrived with refe- 

 rence to the strain of these muscles, so as to 

 enable the slight and delicate structure of the 

 femur (peculiar to all birds), to resist the action 

 of the forces brought to bear upon it, and which 

 exceed in magnitude those acting on the limbs of most quadrupeds. 



12. 31. rectus femoris is not correctly described in any book that 

 I have seen ; and its true nature, and connexion with the muscles 

 of the calf, were discovered by me quite accidentally. I had taken for 

 granted, as a matter of course, that the rectus femoris terminated in the 

 patella ; but, as there were two patellas, I wished to know in which of 

 them the muscle terminated : on dissection, to my surprise, I found that 

 instead of ending in either patella, its tendon passed in a groove over 

 and between them both, and, turning outwards and backwards into the 

 calf of the leg, became provided with a second muscular belly, which 

 formed one of the portions of the flexor digitorum magnus, the con- 

 joined tendon of which passed under the heel, and terminated in the 

 plantar surface of the toe. 



The rectus femoris, with its tendon, is therefore truly a digastric 

 muscle, upwards of five feet in length (Fig. 9), and has its origin in the 



Fig. 8. 



IKNER SIDE OF LEFT FEMUR 

 OF OSTRICH. . 



«, Insertion of ligamentum 

 teres. 



b, iliacus. 



c, Origin of vastus interims, 



No. 1. 



d, Insertion of semimembra- 



nosus. 



e, Origin of crurceus. 



f, „ vastus internus, 



No. 2. 



g, ,, tibialis anticus. 



