64 



TOPOGRAPHICAL AX ATOMY OF 



Very slender dorsal metacarpal arteries (aa. nietacarpea dorsalis 

 medialis et lateralis) will be found in the shallow grooves at the line 

 of junction of the second and third and third and fourth metacarpal 

 bones. These vessels arise from the rete carpi dorsalis, and are con- 

 nected with the volar metacarpal arteries by small communicating 

 vessels that cross the surface of the second and fourth metacarpal 

 bones close to their bases. 



The dorsal metacarpal arteries can often be followed to a union 

 with the volar arteries in the distal third of the metacarpus. 



M. extensor digitoruni communis 



First phalanx. 



V. digitalis medialis. 



X. volaris medialis 

 (ramus dorsalis). 



A. digitalis volaris medialis. 



N. volaris medialis 

 (ramus volaris). 



M. flexor digitoruni 

 profundus. 



Lig. sesamoideum rectum. 



V. digitalis lateralis. 



M. flexor digitoruni sublimis. 



~N. volaris lateralis (ramus 

 dorsalis). 



A. digitalis volaris lateralis. 



X. volaris lateralis (ramus 

 volaris). 



Fig. 45. — Section across the First Phalanx at the Level indicated by L in Fig. 30. 



The common digital artery (a. digitalis communis) is the direct 

 continuation of the median, and follows the medial border of the flexor 

 tendons behind the carpus and metacarpus. As the level of the 

 sesamoid bones is approached, the artery gains (approximately) the 

 middle line of the limb by sinking between the middle interosseous 

 muscle and the tendon of the deep flexor. Immediately proximal 

 to the sesamoids the common digital divides into the medial and 

 Uttered volar digital arteries (aa. digitalis volaris medialis et lateralis). 



Each volar digital artery follows the appropriate border of the 

 flexor tendons, passes under the cartilaginous appendage of the third 

 phalanx, and finally enters the volar foramen of the third phalanx. 

 Both arteries contribute similar branches to the digit. Some of these 

 are distributed on the dorsal, some on the volar aspect. Like 

 branches of the two arteries anastomose with each other in the 

 middle line of the limb, and thus produce a series of vessels that 

 encircle the digit at different levels. Small twigs are also furnished 

 for joints, tendons, " ergot," and skin. 



The named branches of the digital arteries are as follows: — 



