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  Section: Anatomy of Vertebrate Animals » The Muscles and the Viscera
 
 
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Muscles of the Antebrachium and Crus

 
     
 

On the dorsal aspest of the fore-limb, as of the hind-limb, certain muscles arise in part 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 forelimb, the triceps extensor and the supinator brevis; in the hind-limb, the quadriceps extensor.

There is this difference between these two homologous 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 portion, as supinator brevis, into the pre-axial bone (radius); whereas, in the hindlimb, 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 humerus, and inserted into the two bones of the forearm. On the pre-axial side are two muscles; one double-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 brachialis 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-membranosus and semi-tendinosus, pass from the ischium to the tibia, and replace, without exactly representing, the supiinator longus. Corresponding with the brachialis anticus is the short head of the biceps femoris, arising from the femur, and inserted into the post-axial bone of the leg, the fibula. The long head of the biceps femoris, which proceeds from the ischium, appears to have no representative in the fore-limb.

In the fore-limb, a muscle, the pronator teres, passes obliquely fiom the post-axial condyle of the humerus to the radius, in the hind-limb, a corresponding muscle, the poplitanous proceeds from the post-axial condyle of the femur to the tibia. The pronator quadnitas, which passes from the ulna to the radius, has its analogue, in some Marsupialia and Reptilia, in muscles which extend from the fibula to the tibia.


 
     
 
 
     



     
 
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