68 LANDMARKS MEDICAL AND SURGICAL. 



the splitting of the palmar fascia into its four slips. The 

 transverse metacarpal ligament lies in the same line with it. 

 Again, a little below this furrow, the digital arteries bifurcate 

 to run along the opposite sides of the fingers. 



149. Xnterdigital folds. By pressing upon the interdi- 

 gital folds of skin, we can feel the transverse ligament of the 

 fingers, which prevents their too wide separation. The skin 

 of these folds is much thinner on the dorsal than the palmar 

 aspect ; hence deep-seated abscesses in the palm very fre- 

 quently burst on the back of the hand. 



1 50. Digital furrows. Concerning the transverse furrows 

 on the palmar surface of the fingers, notice that the first 

 furrows, close to the palm, do not correspond with the meta- 

 carpal joints. The second and third furrows do correspond 

 with their respective joints. 



The slight depression observable between the ball of the 

 thumb and that of the little finger corresponds with the 

 middle of the anterior annular ligament 



151. Palmar arterial arches. In opening abscesses in 

 the palm, it is important to bear in mind the position of the 

 large arterial arches which lie beneath the palmar fascia. 

 The line of the superficial palmar arch crosses the palm 

 about the junction of the upper with the lower two- 

 thirds that is, in the line of the thumb separated widely 

 from the fingers. From this, the digital arteries run straight 

 between the shafts of the metacarpal bones towards the clefts 

 of the fingers. Incisions, therefore, to let out pus beneath the 

 palmar fascia may safely be made in the lower two-thirds of 

 the palm, provided they run in the direction of the middle 

 line of the fingers. The deep palmar arch lies half an inch 

 nearer the wrist than the superficial. 



152. Digital arteries. As the digital arteries run along 

 the 'sides of the fingers, the incision to open a thecal abscess 

 should be made strictly in the middle line. It should be 

 made not over but between the joints, since the sheath is 

 strongest and thickest over the shafts of the phalanges, and 

 therefore more likely to produce strangulation of the enclosed 

 tendons. 



