THE LIMBS OF THE HORSE 61 



Some few scattered bundles of muscular tissue, more obvious in the 

 young than in the old, still remain as a record of its ancestral history. 

 The strong, flattened tendinous band into which the muscle has been 

 transformed lies between the flexor tendons and the groove-like space 

 formed by the three metacarpal bones. Its origin, confused with the 

 volar carpal ligament, is from the posterior surface of the distal row 

 of carpal bones and the neighbouring part of the third metacarpal. 



In the distal third of the metacarpus the band divides into two 

 limbs, each of which is attached to a sesamoid bone. A continuation 

 of each limb passes obliquely across the border— medial or lateral, as 



Third metacarpal bone. M. extensor digitonim communis. 



H EDI At 



A. metacarpea dorsalis 

 lateralis. 



Fourth metacarpal bone. 



ute^/^l 



A. metacarpea dorsalis. 

 medialis. 



Second metacarpal ^k'^ ^-•'■'^{••■■.^^pc=^^^^^' _ \.-?i*?»;-,\]Jl^_-3]. extensor digit] 



bone. - ^-4V-' ' ' V-'''- If '~-'^:>c=:::f\--'-' ■'■//' I ( quinti. 



. „ . , . ... ^^^^^^^^^^Z" Z. ^'".— ' ' ><.o;^^ ^'^,M. interosseus. 



A. metacarpea volans medialis.:^ ^^>f, S^P*^ - \ Cr";<^ 



V. digitalis communis. ''' ^-^ ''(2Bl''V_ -""^s jQ.'CW^ ''^^ ir 



M. flexor digitorum profundus (caput W^/--^^======e<i?W~X ~^ i.";!'"S'''^" '^'"^ 



tendineum). ^''^>}Y<>k" t ^;"vW'~^ N lateralis. 



A. digitalis communis.' mL . O^.,^?;^^ '..^ ': a. metacarpea volaris lateralis, 



N. volaris lateralis. 

 N. volaris medialis. ^ ^"'*'^i^M!^iS^^0^ ^M. flexor digitorum profundus. 



M. flex')r digitorum sublimis. 



Fig. 40. -Section across the Metacarpus at the Level indicated by G in Fig. 30. 



the case may be — of the first phalanx to reach the dorsal aspect of this 

 bone and here join the tendon of the common extensor of the digit. 



The strong tendinous structure representing the middle interosseous 

 muscle obviously serves as a mechanical stay when the weight of the 

 body is sustained by the limb, and thus prevents over-extension of 

 the metacarpo-phalangeal joint, while, at the same time, removing strain 

 from the flexor muscles. 



Arteries of the metacarpus and digit. — As has been seen, the 

 median artery terminates as the common digital, and, at the same 

 point, contributes the medial and lateral volar ^ metacarpal arteries. 



The medial volar metacarpal artery (a. metacarpea volaris medialis) 

 follows the tendon of the flexor carpi radialis very closely in its course 

 down the medial posterior part of the carpal region. Having distri- 

 buted twigs to the rete carpi dorsalis, the artery sinks into the cleft 



1 Vola [L.], the palm. 



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