418 MUSCLES. 



cess of the scapula, in common with the short head of the bi. 

 ceps muscle. 



It is inserted, tendinous and fleshy, into the internal side of 

 the middle of the os humeri, by a rough ridge, just below the 

 tendons of the latissimus dorsi and teres major, and in front of 

 the brachialis externus or third head of the triceps. The lower 

 end of this muscle is attached to the inter-muscular ligament of 

 the internal side of the os humeri, which separates the brachi- 

 alis interims from the third head of the triceps. 



This muscle draws the arm upwards and forwards.* 



The Brachialis Interims, 



Is situated immediately beneath the biceps, and is concealed 

 by it, excepting its outer edge. It has a bifurcated fleshy ori- 

 gin from the middle front face of the os humeri on each side 

 of the insertion of the deltoid, and its origin is continued fleshy 

 from this point downwards, from the whole front of the bone 

 to within a very small distance of its articular surface. 



It is inserted, by a strong short tendon, into the rough surface 

 at the root of the coronoid process of the ulna. A bursa some- 

 times exists between the tendon of the brachialis internus, that 

 of the biceps, the supinator brevis, and the elbow joint. 



The brachialis flexes the fore arm, and, by passing in front of 

 the elbow joint, strengthens the latter very much. Its lower 

 part lies under the tendon of the biceps, and between the pro- 

 nator teres and the supinator longus.f 



* Varieties. This muscle being generally penetrated by the musculo-cuta- 

 neous nerve, the perforation thus made sometimes exists as a fissure, extending 

 the length of the lower half of the muscle; on other occasions the fissure is so 

 long as to divide the muscle completely into two. 



f Varieties. Sometimes, at its external margin, there exists a smaller brachia- 

 lis internus muscle, which arises from about the same point of the humerus, and 

 is inserted into the same part of the cubitus. Sometimes it detaches a fasciculus 

 which joins the biceps muscle. Sometimes its posterior part is distinct from the 

 anterior. Sometimes a fasciculus of it runs along the supinator longus of the fore 



