THM EXTERNAL ILIAC ABTEBIES. 553 



covers a portion of its surface, enlaces it with numerous filaments, and is so 

 closely associated with it in all its flexuosities as to form but a single cord 

 with it. 



" In front, it is margined, though for a short distance, by its satellite 

 vein, which for the whole of its track rests on the lateral faces of the two 

 fio-st phalanges. 



" At its upper part, near its origin, and on the lateral portions of the 

 metacarpo-phalangeal articulation, the digital artery is crossed from behind 

 to before by the anterior branch of the plantar nerve, and it is covered for 

 the whole of its extent by the fascia which continues the proper tunic of the 

 plantar cushion, whose lateral ligamentous band cuts its direction obliquely 

 from above to belovF and behind to before, at the middle portion of the first 

 phalanx.'" 



Collateral divisions. — These are : 1. At the fetloct, numerous fine 

 branches distributed to the metacarpo-phalangeal articulation, but par- 

 ticularly to the sesamoid sheath, and the tendons lodged in it. 



2. To the environs of the upper extremity of the first phalanx, a slightly 

 ascending and sometimes voluminous tsvig, for the tissue of the ergot (the 

 horny tubercle behind the fetlock). 



3. Towards the middle of the same bone, the vessel named by Peroivall 

 the perpendicular artery, and correctly so, for it arises at a right angle from 

 the digital artery to divide almost immediately afterwards into two series of 

 ramifications — anterior and posterior. The anterior branches are in nearly 

 every instance two principal : one ascending, passing beneath the check 

 band of the extensor tendon, and climbing to the capsular ligament of the 

 fetlock joint to meet the arterial divisions furnished directly to that ligament 

 by the collateral artery of the cannon ; the other descending, which reaches 

 the side of the second phalanx, where its ramuscules anastomose with the 

 coronary circle and the circumflex artery of the coronary substance (cushion). 

 The posterior ramifications consist most frequently of two principal branches, 

 — one ascending, the other descending ; these insinuate themselves between 

 the flexor tendons and the sesamoid ligaments, to be distributed to these 

 organs, but especially to the synovial membrane lining the large sesamoidean 

 sheath. Sometimes it is seen to arise alone from the digital artery. It must 

 here be noted, that the divisions furnished by the anterior branches of this 

 perpendicular artery communicate with those of the opposite side in front 

 of the first phalanx, either above or below the principal extensor of the 

 digit ; and that the posterior branches exhibit a series of analogous anasto- 

 moses. The body of the first phalanx is therefore enveloped on every side 

 by an arterial plexus. 



4. At different elevations on the first and second phalanges, several 

 tendinous and cutaneous twigs, which are of no importance. 



5. The artery of the plantar citshion, which arises at the superior border 

 of the lateral cartilage, is directed obliquely backward and downward, and 

 placed within the posterior border of that cartilage, to be distributed to 

 the middle portion of the complementary apparatus of the third phalanx, as 

 well as to the villous tissue and the coronet. The branch expended in the 

 latter sometimes proceeds, directly from the digital artery; it is a very 

 remarkable vesssel, is inflected from before to behind, crossing the posterior 

 border of the pedal cartilage, creeping on the internal face or in the texture 

 of the skin, a little above the coronet, parallel with that portion of the 



1 2r. Souley. — ' Traite de I'Organisation du Pie3 du Cheval.' Paris, 1S51. 



