DISEASES OF TENDONS. 141 



sheath may be widespread. Should the haematoma suppurate, 

 the pus will at first be confined by the sheath of the rectus, but 

 may track for a considerable distance within it, leading some- 

 times to most troublesome sinuses. 



The biceps cubiti arises by two heads, the long from the upper 

 border of the glenoid fossa, the short from the tip of the 

 coracoid process. The long tendon is a part of the muscle 

 which not infrequently gives way, and its passage through the 

 joint over the head of the humerus conduces to its laceration, 

 particularly when the tendon has been thinned by friction in 

 cases of osteo-arthritis. It may then acquire an attachment 

 lower down in the bicipital groove. The short head is rarely 

 torn. The belly of the muscle may be ruptured in very forcible 

 flexion against much resistance. The muscle is inserted by means 

 of a tendon into the posterior part of the bicipital tubercle of the 

 radius. In some cases of strong action, the tendon may be torn 

 away from its attachment, and may even drag a piece of bone off 

 with it. 



The plantaris, arising from the back of the femur just above 

 the external condyle, has a small belly, terminating in a long, 

 slender tendon which is inserted into the tendo Achillis or into 

 the inner side of the posterior surface of the os calcis. The 

 tendon may be snapped in wrestling, slipping on the stairs, 

 tennis, etc. 



The quadriceps extensor cruris. Sometimes, and for the same 

 reasons that the patella is transversely fractured by muscular 

 action, the tendon of the quadriceps may be torn across close 

 above its insertion, the patella remaining intact. 



DISEASES OF TENDONS. 



Many tendons, especially when long as those of the flexors 

 and extensors of the fingers and toes, are surrounded by a 

 fibrous sheath lined by a synovial membrane. Such tendons 

 from their anatomical position are liable to considerable action, 

 and often to external violence. 



