THE LIMBS OF THE HORSE 57 



third phalanx. At the proximal end of the metacarpus the tendon is 

 placed decidedly lateral to the middle line of the limb. This position, 

 however, is gradually changed until, by the time the metacarpo- 

 phalangeal joint is reached, the tendon is equidistant from the two 

 borders of the limb. In the neighbourhood of this joint, also, as well 

 as in the digit, the tendon is wider and thinner than elsewhere. It is 

 intimately connected with the capsules of the several joints associated 

 with the phalanges, but a synovial bursa of limited extent is placed 

 between the tendon and the capsule of the metacarpophalangeal 

 articulation. 



In the proximal third of the metacarpus a strong fascial band from 

 the lateral aspect of the carpus is connected with the extensor tendon, 

 and about the middle of the first phalanx each border of the tendon is 

 joined by a strong oblique offset from middle interosseous muscle. 



M. EXTENSOB digiti QUiNTi. — After passing through the liga- 

 mentous canal at the lateral border of the carpus, the tendon of this 

 muscle pursues an oblique course along the dorsal-lateral part of the 

 metacarpal bone and is inserted to the proximal part of the dorsal 

 (anterior) surface of the first phalanx. 



Soon after its entry into the metacarpal region the tendon is 

 joined by the thin tendon of the muscle of Phillips and a strong fascial 

 band from the lateral part of the carpus. Compact hitherto, the tendon 

 now broadens, and not infrequently divides into more or less isolated 

 bundles of fibres. A small synovial bursa lies beneath the tendon as it 

 crosses the head of the third metacarpal bone and the joint between 

 this bone and the first phalanx. 



M. flexor digitorum SUBLIMIS. — The tendon of the superficial 

 digital flexor demands careful examination. In the first place it will be 

 noticed that it passes through fascial sheaths — lined by synovial tendon 

 sheaths — at the carpus and in the region of the metacarpo-phalangeal 

 joint. 



The tendon leaves the forearm by running through the roughly 

 triangular passage or canal bounded by the carpus in front, the accessory 

 carpal (pisiform) bone laterally, and the transverse ligament of the 

 carpus on the volar side. In its passage through the canal the flexor 

 tendon is enclosed in a synovial investment (vagina carpea) the extent 

 of which is to be determined by dissection. 



In the digital region the tendon traverses the canal formed by the 

 phalanges (and the superposed ligaments) and the specialised fascial 

 bands (fibrous tendon sheaths) already noted, and is surrounded by a 

 second synovial or mucous sheath. 



Turning now to the tendon itself, it will be found that until it 



