THE BRACHIAL OR AXILLARY ARTERIES. 657 



collateral artery of the cannon — a branch that crosses the foramen towards the inferior ex- 

 tremity of the bony diaphysis. If it is desired to ascertain the signification of these interosseous 

 arteries, in their relation to the elements composing the foot of Ruminants, we readily recognize: 

 in the posterior median artery, the interosseous palmar of the two great digits ; in the posterior 

 lateral arteries, the interosseous palmar, intermtdiates to these middle digits, and the rudi- 

 mentary lateral digits represented by the ergots, or dew claws ; and in tlie single autfrior 

 artery, the dorsal interosseous of the two great digits. We may even prove, by a more minute 

 examination, the existence of dorsal interosseous arteries corresponding to the lateral palmar 

 interosseous vessels. 



11. Collateral artery of the cannon. — This artery follows the same track as in the Horse, as 

 far as the lower third or fourth of the metacarpus. Arrived at this point, it gives off — as in 

 the Horse — a branch the divisions of which communicate with the interosseous arteries, and 

 are continued by the digital arteries, three in number— a middle and two lateral. 



a. The communicating branch with the metacarpal interosseous arteries, very often arises 

 from the internal digital artery. 



It is insinuated between tiie divisions of the suspensory ligament, and ascends on the 

 posterior face of the metacarpus, breaking up into a number of branches which nearly all join 

 the precited arteries, or even the lateral digital, in having a variable and complicated arrange- 

 ment which it is neeilless to notice here. One of tliese branches — a true perforating artery, 

 traverses the inferior extremity of the cannon bone, and ascemls in its anterior groove to join 

 the anterior interosseous artery, after detaching ramuscules to the metacarpo-phalangeal 

 articulation. 



h. The middle digital artery represents, in its dimensions, the continuation of the collateral 

 artery of the cannon, and is a very voluminous vessel. It is at first inflected backwards and 

 outwards, to be placed on the posterior face of the perforatus tendon ; then it descends into 

 the interdigital space by passing behind the sesamoid bursa, beueatli the ligament uniting the 

 two claws. Reaching the inferior extremity of the first phalanx, it divides into two ungual 

 arteries — one for each digit, which are inflected forwards, pass beneath the internal ligament 

 common to the two interphalangeal articulations, and enter by the foramen at the inner side 

 of the pyramidal process, into the internal sinus of the third phalanx, where each ramifies in 

 the same manner as the plantar ungual arteries of the Horse. 



Several collateral branches, remarkable for the richness of their arborizations, escape from 

 this median artery of the digits and its terminal divisions. The most important of these are: 

 1. At the middle of the first phalanx, two short transverse branches— a right and left, passing 

 beneath the flexor tendons, and going from the median digital artery to the lateral arteries of 

 the digits. 2. Nearly at the same point, a single artery which traverses the interdigital space 

 from behind to before, to pass between the two tendons of the common extensor of the phalanges, 

 ■whence it ramifies on the anterior face of the digits by ascending alongside the anterior median 

 vein, and anastomosing with a descending branch of the perforating artery which crosses the 

 inferior extremity of the metacarpus. 3. A double branch analogous to the artery of the 

 plantar cushion of the Horse, having its origin at the terminal extremity of the digital artery, 

 often arising from the ungual artery, either on one side or b"th, ami communicating, by a 

 transverse branch, with its homologue ; it is directed backward and downward on the bulb of 

 the heel, where it forms an anastomotic arch with the lateial digital aitery ; from the convexity 

 of this arch, which is turned downwards, there escapes a large number of reticulating ramus- 

 cules, which go to the keratogenous membrane and the plantar cushion. 



c. The lateral digital arteries are distinguished into internal and external. The first has 

 its origin at the bend formed by the collateral of the cannon, when that vessel is inflected on 

 the posterior face of the perforatus tendon to become the median digital artery, most frequently 

 in common with the branch the divisions of which join the metacarpal interosseous aiteries. 

 The second commences a little further ofl", after having received a branch from eitner this 

 communicating artery, or from the external interosseous palmar ; it is not rare to see it 

 entirely formed by one of these branches, or by the two together. Whatever may be their 

 point of origin, the lateral digital arteries descend on the eccentric side of the digits, outside 

 the flexor tendons, and terminate in anastomosing by inosculation with the artery of the 

 plantar cushion. Among the collateral branches emanating from these arteries, there ought to 

 be distinguished that which goes to the ergot, and the transverse branch thrown across between 

 each, as well as the median digital artery.' 



' In several instances, we have seen the lateral digital arteries stop at this transverse 

 anastomosis, which then received them entirely- 



