THE MUSCLES OP THE LIMBS. 51 



logue in tlie uppei- extremity of tlie liigher Vertebrata, unless 

 it be the so-called coracobrachialis, wliich arises from the 

 inner surface of the coracoid in many Sauropsida. 



Muscles of the Antebrachiuvi and Cms. — Oil the dorsal asi^ect 

 of the fore limb, as of the hind limb, certain muscles arise 

 in j)art from, the arch, and, in part, from the bone of the 

 proximal segment of the limb, and go to be inserted into 

 the two bones of the second segment. These are, in the 

 fore limb, the triceps extensor and the supinator brevis ; in 

 the hind limb, the quadriceps extensor. 



There is this difference between these two homologoiis 

 groups of muscles — that in the fore limb, the principal 

 mass of the muscular fibres goes, as the triceps, to be 

 inserted into the post-axial bone (ulna), and the less por- 

 tion, as supinator brevis, into the pre-axial bone (radius) ; 

 whereas, in the hind limb, it is the other way, almost the 

 whole of the muscular fibres passing, as the quadriceps, to 

 the pre-axial bone (tibia), the tendon commonly developing 

 a sesamoid patella ; while only a few fibres of that division 

 of the quadriceps which is called the " vastus externus " pass 

 to the post-axial bone (fibula). 



On the ventral aspect, the fore limb presents three muscles, 

 arising either from the pectoral arch, or from the hiimerus, 

 and inserted into the two bones of the forearm. On the 

 pre-axial side are two muscles ; one dou-ble-headed, the biceps, 

 arising from the scapula and the coracoid, and inserted into 

 the radius. A second, the supinator longus passes from the 

 humerus to the radius. On the post-axial side, the b'ra- 

 chialis anticus arises from the humerus, and is inserted into 

 the ulna. The hind limb has two muscles, the sartorius, 

 arising from the ilium, and the gracilis, from the pubis, 

 in place of the biceps brachii, and inserted into the pre-axial 

 bone, the tibia, which corresponds with the radius. Two 

 other muscles, the semi-menibranosus and semi-tendinosiis, 

 pass from the ischium to the tibia, and replace, without 

 exactly representing, the supincdor longus. Corresponding 

 with the brachialis anticus is the short head of the biceps 

 femoris, ai-ising from the femur, and inserted into the post- 



