122 THE UPPER EXTREMITY 



digitorum sublimis, the flexor digitorum profundus, the tendon 

 of the flexor pollicis longus, and the median nerve. The 

 relation of the tendon of the flexor carpi radialis to the 

 transverse carpal ligament is peculiar. It pierces the lateral 

 attachment of the ligament, and proceeds distally in the 

 groove of the os multangulum majus in a special compartment 

 provided with a special mucous sheath. 



Mucous Sheaths of the Flexor Tendons. As the flexor 

 tendons and the median nerve pass through the carpal tunnel 

 they are enveloped in two mucous sheaths, which at the same 

 time line the walls of the canal, and thus greatly facilitate the 



Median nerve 



Lig. carpi transversunv(O.T. a nt. annular lig.) 



Sheath of flexor pollicis longus . Tendons of flexor digitorum sublimis 



Tendon of flexor pollicis longus ' > ,^ . .. . . 



, , ... j- i- i __ *=T=--*4iX_ Cavity of synovial sheath 



Sheath of flexor carpi radialis 



Tendon of flexor carpi radialis 



Tendons of flexor digitorum profundus 



FIG. 48. Diagram illustrating the relation of the Synovial Sheath 

 to the Flexor Tendons. 



free play of the tendons behind the transverse carpal liga- 

 ment. As already stated, these sheaths are two in number. 

 One is wrapped around the tendon of the flexor pollicis longus, 

 the other invests the tendons of the flexor digitorum profundus 

 and flexor digitorum sublimis. Both are prolonged proximally 

 into the forearm for an inch or more, and both are carried 

 distally into the palm in the form of diverticula upon the 

 diverging tendons. The diverticula in relation to the tendons 

 which go to the index, middle, and ring fingers, end near the 

 middle of the palm. Those upon the tendons of the thumb 

 and little finger, however, are prolonged distally into the 

 digits, and line the fibrous sheaths which confine the tendons 

 upon the volar aspects of the phalanges. 



It is not likely that these mucous sheaths have been preserved intact 

 throughout the previous dissection of forearm and palm ; but should they 



