THE ARTERIES 177 



operation of tenotomy of the superficial and deep flexors of the digit, and 

 the method of dealing with the vessel whilst performing these operations 

 has already been indicated. It is not uncommonly involved in serious 

 cases of low speedy cutting. Should it be necessary to ligature the 

 artery, a vertical incision should be made at the required level a 

 quarter of an inch in front of a vertical line drawn through the seat of 

 incision in plantar neurectomy. 



The Internal Digital Artery. — From the point of division of the large 

 metacarpal artery this vessel passes to the inner aspect of the limb, where 

 it appears superficially between the inner division of the suspensory 

 ligament and the perforans tendon. It runs vertically across the inner 

 aspect of the fetlock, crossing the anterior digital nerve. It is here 

 placed between the posterior digital nerve and the digital vein, the latter 

 being in front of the artery. It is next crossed by the middle digital 

 nerve, and below the fetlock it is found again on the edge of the 

 perforans tendon after the latter has emerged from the ring formed by 

 the tendon of the perforatus. Along the edge of this tendon the artery 

 passes to the inner aspect of the internal lateral cartilage, where it 

 terminates by dividing into the plantar and preplantar (ungual) arteries. 



The External Digital Artery . — This artery passes across the back of the 

 limb from the bifurcation of the large metacarpal artery, and appears on 

 the outer aspect between the perforans tendon and the outer division of 

 the suspensory ligament. Its subsequent course, relations, and termina- 

 tion correspond with the description we have given of the internal 

 digital artery. 



Collateral branches of the digital artery : 



1. Branches are distributed to the fetlock joint and to the great 

 sesamoid sheath. 



2. The Perpendicular Artery of the F astern. — This leaves the digital 

 artery about midway down the first phalanx. It arises at right angles 

 and is crossed by the digital vein and middle digital nerve. Near its 

 origin from the digital artery it gives off ascending and descending 



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