550 THE ARTERIES. 



satellite branct of the sciatic nerve, and a thin twig which descends with 

 the external saphena nerve into the hollow of the hook, where it meets, like 

 the preceding, a branch of the posterior tibial artery. Several of the 

 ascending branches pass along the great femoro-popliteal nerve, and all 

 anastomose either with the deep femoral, or with the isohiatic arteries in the 

 substance or interstices of the ischio-tibial muscles (JFig. 277, 19). 



TERMINAL BRANCHES OF THE POPLITEAL AE^EKY. 



1. Posterior Tibial Artery. (Fig. 277, 21.) 

 Preparation.— Folloin the indications furnished by figure 277. 



At first situated deeply behind the tibia, beneath the popliteal muscles 

 and the oblique and deep flexors of the phalanges, this artery descends 

 towards the hoUow of the hock, becoming gradually more and more super- 

 ficial, and lying below the tibial fascia, behind the tendon of the oblique 

 flexor muscle, along with its satellite vein. Arriving at the apex of the 

 OS calcis, it crosses the precited fascia, describes an S curve, and, along 

 with the sciatic nerve, passes beneath the tarsal arch ; at the astragalus it 

 separates into two terminal branches — the plantar arteries. 



Collateral branches. — We cite : 1, Numerous branches destined to the 

 posterior deep tibial muscles ; 2, The medullary artery of the tibia ; 3, The 

 tarsal articular arteries, a principal of which, with a large venous arch, 

 passes under the perforans, near the inferior extremity of the tibia, to be 

 distributed outside the tarsus by descending ramuscules and ascending tvidgs, 

 which extend as far as the gastrocnemii tendons ; 4, A superficial ascending 

 branch, arising ordinarily from the second inflexion 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, and whose ramifications, nearly all 

 subcutaneous, are scattered, within and without, on the sides of the hock 

 and the inferior extremity of the thigh. 



Terminal branches. — -The 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, and form a kind of deep arcade across the upper extremity of the 

 suspensory ligament of the fetlock : that is, from the post-metatarsal fibrous 

 band which 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 very fine twigs accompanying the plantar nerves, and 

 creeping by the side of the flexor tendons to the sesamoid groove, where 

 they inosculate with the collaterals of the digit (Figs. 277, 24; 278 8)- 

 2, Two deep branches constituting the plantar interosseous' arteries,' iis- 

 tmguished mto external and internal. The first is only an extremely fine 

 vascular thread, very uncertain in its disposition, and possesses no other 

 importance m Solipeds than representing, in a rudimentary state an 



