TBE EXTERNAL ILIAC ARTERIES. 555 



fissure, whicli it crosses from before to behind, and terminates near its 

 anterior extremity by several divisions that bury themselves in the os 

 pedis. In its course, it distributes : 1, Before passing into the sub-basilar 

 notch, a deep retrograde branch destined to the bulb of the heel and the 

 villous tissue ; 2, Immediately after leaving that notch, a second retrograde 

 branch, whose divisions pass backward, behind the great circumflex artery of 

 the pedal bone ; 3, During its passage in the preplantar fissure, several ascend- 

 ing and descending branches which ramify in the laminal tissue ; the first 

 anastomose with the descending divisions of the coronary circle and the 

 circumflex artery of the coronary cushion. 



b. The plantar xmgual artery ought to be regarded as a continuation of 

 the digital artery, because of its volume and direction. Lodged at first, 

 with a fine nervous branch, in the plantar fissure, it afterwards enters the 

 canal of the same name, and thus penetrates into the semilunar sinus of the 

 OS pedis, where it anastomoses by inosculation with the opposite artery, 

 forming a deep vascular arcade which we designate the plantar arcade or 

 circle, or, after M. H. Bouley, the semilunar anastomosis (Fig. 283, 12). 



Two orders of branches emanate from the convexity formed by this 

 anastomotic loop. The ascending order " irradiate in the spongy framework 

 of the third phalanx, and like so many hair-roots, escape by numerous open- 

 ings from its anterior face, where they form a very intricate plexus by anasto- 

 mosing, in the texture of the laminal tissue, with the extreme divisions of the 



anterior branch of the digital artery and those of the coronary circle 



It is to these divisions that Spooner has given the name of anterior laminal 

 arteries'' — H. Bouley. 



The descending order, much more considerable, named by Spooner (W. C, 

 of Southampton) the inferior communicating arteries, arise at a right angle from . 

 the anterior circumference of the semilunar anastomosis, traverse in a diver- 

 gent manner the tissue of the phalanx, and make their exit by the large fora- 

 mina situated a little above the inferior border of the bone, where they furnish 

 a multitude of ascending ramuscules which concur to form the arterial net- 

 work of the laminal tissue. " Then they anastomose transversely by a 

 succession of little arcades which are thrown from one to the other, and in 

 this way give rise to a great circumflex canal which follows the contour of the 

 parabolic curve exhibited by the thin border of the os pedis, on its inferior 

 face." — H. Bouley. This vascular arcade, which we purpose naming the in- 

 ferior circumflex artery of the foot, to distinguish it from the circumflex of the 

 coronary cushion, is joined by its extremities to the preplantar artery, in the 

 same manner that the latter circumflex is united to the artery of the plantar 

 cushion. From its concavity it throws off some fourteen or fifteen con- 

 vergent branches, which are destined to the villous tissue of the sole. 



DIFFEEENnAl CHAEACTEHS OP THE KXTEENAL ILIACS IN OTHEE THAN" SOLIPED ANIMALS. 

 1. External Iliac Arteries of Ruminanls. 



In the Ox, apart from the considerable volume of the great muscular arteries of the 

 thigh, the crural trunk, as well aa the femoral and popliteal arteries continuing it, 

 comport themselves almost the same as in the Horse. It is only when we reach the 

 posterior and anterior tibial arteries that we find some peculiarities worthy of notice. 



Posterior tibial artery. — Much more voluminous than that of Solipeds, this artery follows 

 the same track, and terminates in an analogous manner : forming at its lower extremity 

 two plantar branches, wliieh anastomose with the perforating pedal artery behind the 

 superior extremity of the principal metatarsal bone, and beneath the suspensory ligament. 

 But these two branches are f^r from possessing the same volume ; the internal is in- 

 comparably the largest, and appears to be the direct continuation of the posterior tibial 

 artery. 



