THE MUSCLES OF THE UPPER EXTREMITY. 115 



33) muscle arises by a tendon common to it and the 

 tensor patagii brcvis from the supero-mesial line of 

 the head of the corresponding clavicle. This tendon 

 is flat and thin, being closely approximated to the 

 head of the coracoid and the outer angle of the 

 pectoralis major muscle. The tensor patagii longus 

 soon becomes muscular, however, after leaving its 

 origin, to form a slender, spindle-shaped belly about 3 '5 

 centimetres long. From its distal apex then a tendon 

 is given off, which runs in the marginal duplicature of 

 the patagium, and with which fibro- elastic membrane 

 it is intimately connected. This tendon increases in 

 calibre, and for more than its entire middle third it 

 becomes in turn of a fibre-elastic structure. Finally 

 passing over the end of the radius and to the inner 

 side of the tendon of the extensor metacarpi radialis 

 longus, it is attached to the os radiale of the carpus, 

 and the fascia w r hich binds down the other tendons on 

 the anterior aspect of the wrist-joint. 



68. The tensor patagii brevis arises from the head 

 of the clavicle, as described for the last muscle, by a 

 common tendon. The muscular portion of this short 

 tensor of the patagiurn is very considerably broader and 

 longer than that of the long tensor of the membrane 

 in question. It also overlies the former to a certain 

 extent near their common origin, and is pointed 

 downward towards the elbow instead of outwards 

 towards the carpus. Its tendon is straight, slender, and 

 nearly of uniform calibre. At about 1'5 centimetres 

 from the distal end of the humerus it meets the 

 extensor metacarpi radialis longus muscle of the 

 antibrachium. There its tendon bifurcates, and the 

 shorter and distal-projecting bifurcation is soon merged 

 into the fascia of the muscle just alluded to, of the 



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