THE EXTERNAL ILIAC ARTERIES. 635 



ordinarily from the second inflection of the S curvature formed by the artery 

 at its lower extremity, situated in the hollow of the hock, anastomosing with the 

 saphena artery, as well as with the satellite popliteal branch of the sciatic nerve, 

 the ramifications of which, nearly all subcutaneous, are scattered within and 

 without on the sides of the hock, and the inferior extremity of the thigh. 



Terminal branches. — Tlie two terminal branches of the posterior tibial artery 

 are slender vessels— vestiges of the plantar arteries in Man. Lying on the outer 

 side of the synovial tendinous sheath lining the tarsal groove, they are placed — 

 one within, the other without, the perforans tendon, and descend along with the 

 plantar nerves to the upper extremity of the metatarsus, where they leave the 

 nerves, each to anastomose with the perforating pedal artery, forming a kind of 

 deep arch across the upper extremity of the suspensory hgament of the fetlock 

 — that is, from the post-metatarsal fibrous band that represents the interosseous 

 plantar muscles of tetradactylous or pentadactylous animals. 



In their course, these plantar arteries only distribute some insignificant 

 ramuscules to the tarsal articulations. 



From the convexity of the arch they form in uniting with the perforating 

 pedal artery, arise four long descending branches : 1. Two superficial,, innominate, 

 and veiy fine arterioles accompanying the plantar nerves, and passing by the side 

 of the flexor tendons to the sesamoid groove, where they inosculate with the 

 collaterals of the digit (Figs. 370, 23 ; 371, 8). 2. Two deep branches con- 

 stituting the plantar interosseous arteries, distinguished into external and internal. 

 The first is only an extremely fine vascular twig, very uncertain in its disposition, 

 and possesses no other importance in Solipeds than representing, in a rudimentary 

 state, an artery wliich is of considerable size in other animals. Placed within 

 the external metatarsal bone, it anastomoses, by its inferior extremity, with a 

 branch of the metatarso-pedal artery. The internal interosseous plantar artery 

 may be considered, if we disregard the study of analogies, as the continuation of 

 the perforating pedal artery, which it rivals in volume. It descends to the 

 external side of the internal metatarsal bone, beneath the margin of the suspen- 

 soiy ligament of the fetlock, and terminates a little above the tubercle of the 

 external metatarsal bone, in uniting at a very acute angle with the metatarso- 

 pedal artery. It gives off on its track : the nutrient of the large metatarsal bone ; 

 a small branch to the external interosseous artery ; several ramuscules which 

 cross the posterior border of the internal metatarsal bone to supply the connective 

 tissue, the skin, and the tendons on the large metatarsal bone. 



2. Anterioe Tibial Artery (Fig. 371, 1). 



Preparation. — Expose the artery by removing the anterior muscles of the leg. 



The anterior tibial artery is the largest of the two branches terminating the 

 popliteal trunk. It traverses the tibio-fibular arch, and, with its satellite veins, 

 places itself on the anterior aspect of the tibia, down which it passes by following 

 the deep face of the flexor metatarsi. On reaching the front of the tibio-tarsal 

 articulation, it loses its name and takes that of the pedal (or great metatarsal) 

 artery. 



The anterior tibial artery gives off a great number of collateral branches, 

 which are principally distributed to the tibial muscles. One of them, descending 

 along the fibula, beneath the lateral extensor muscle of the phalanges, clearly 

 represents a trace of the peroneal artery of Man. 



