THE LIMBS OF THE HOKSE 59 



A strong reinforcing tendinous band (caput tendineum) of some 

 physiological importance passes from the back of the carpus, where it 

 is connected with the volar carpal ligament, and joins the deep Hexor 

 tendon about the middle of the metacarpus. 



There can be little question that the tendinous heads of the super- 

 ficial and deep flexors serve the purpose of mechanical stays to the limb 

 and so relieve the fleshy part of these muscles from strain when the 

 standing posture is long maintained. 



The synovial sheaths (vagin.^-:^ mucosae) of tendgisis. — At this 

 stage of the dissection it is advisable to make a general review of the 



il. interosseus. 



M. flexor digitonim subliinis. 



Ji M. Hexor digitonim profundus. 



Fig. 39.— Volar (Posterior) Aspect of the Skeleton of the Digit, with Areas of 

 Muscular Attachment, 



synovial or mucous sheaths, connected with the extensor and flexor 

 tendons, in the carpal, metacarpal, and digital regions. 



Each extensor tendon is furnished with an independent sheath as 

 it plays through the groove provided for it at the distal end of the 

 radius. All the sheaths begin, roughly speaking, on a level with the 

 upper edge of the accessory carpal (pisiform) bone. The sheath of 

 the extensor carpi radialis ends close to the insertion of the muscle. 

 The sheath of the extensor carpi ulnaris belongs to that tendon of the 

 muscle which lies in the oblique groove on the lateral surface of the 

 accessory carpal bone, and terminates near the insertion of this tendon 

 into the fourth metacarpal bone. 



The synovial sheaths of the extensor digitorum communis and 

 extensor digiti quinti end in the proximal fourth of the metacarpus; 



1 Vagina [L.], a sheath. 



