1454 SUKFACE AND SUEGICAL ANATOMY. 



thumb is specially liable to spread upwards into the palm, and thence underneath 

 the transverse carpal ligament into the forearm. 



The pulsations of the radial artery can readily be felt in the distal third of the 

 forearm, midway between the lateral border of the radius and the tendon of the 

 flexor carpi radialis. The course of the vessel is indicated upon the surface by 

 a line extending from the bifurcation of the brachial (J in. distal to the middle of 

 the bend of the elbow) to the tubercle of the navicular, around which, and distal 

 to the tip of the styloid process, the artery winds to the dorsum of the radial side 

 of the wrist ; in the latter situation the vessel, after passing deep to the extensor 

 tendons of the thumb, dips into the palm through the proximal extremity of the 

 first interosseous space. Incisions for opening or resecting the wrist are planned 

 so as to avoid the vessel. 



The proximal third of the ulnar artery is deeply placed, and takes a curved 

 course from the bifurcation of the brachial towards the medial part of the volar 

 surface of the forearm ; the distal two- thirds of the vessel correspond to the distal 

 two- thirds of a line drawn from the front of the medial epicondyle to the radial border 

 of the pisiform bone. The course of the ulnar nerve corresponds to the whole of the 

 above line. 



The median nerve in the forearm may be mapped out by a line extending from 

 a point midway between the centre of the bend of the elbow and the medial epi- 

 condyle, to a point midway between the styloid processes ; in the distal third of 

 the forearm the line follows the medial border of the tendon of the flexor carpi 

 radialis. To evacuate pus spreading deeply up the front of the forearm, the 

 incisions should be made on either side of the line corresponding to the median 

 nerve. The superficial branch of the radial nerve winds to the dorsum of the 

 forearm round the lateral border of the radius deep to the tendon of the brachio- 

 radialis, at the junction of the middle and distal thirds of the forearm. 



The summit, or most distal part of the superficial palmar arch, corresponds to 

 the mid-point of a line extending from the middle of the most distal transverse 

 crease of the wrist to the root of the middle finger ; a line drawn from the radial 

 border of the pisiform bone across the hamulus of the os hamatum, and thence 

 in a curved direction distally and laterally to this point, corresponds to the main 

 or proximal part of the arch; the first and fourth digital branches overlie the 

 fifth and third rnetacarpal bones respectively, while the second and third overlie 

 the fourth and third interspaces respectively. The deep arch lies almost trans- 

 versely, midway between the distal border of the transverse carpal ligament and 

 the superficial arch. The radialis indicis corresponds to the radial border of the 

 index -finger. 



The ulnar nerve and the commencement of its two divisions lie immediately to 

 the medial side of the superficial palmar arch, so that the pisiform and the hamulus 

 of the os hamatum are the guides to the nerve. The median nerve emerges from 

 under the transverse carpal ligament opposite the medial edge of the thenar 

 eminence, while the digital branches to the thumb follow its distal margin. 

 Incisions for the removal of foreign bodies may therefore be made into the 

 thenar with greater freedom than into the hypo-thenar eminence. 



. Incisions to evacuate deep-seated pus in the palm may be made in one or more of 

 the following situations : (1) over the distal two-thirds of the second metacarpal bone ; (2) 

 over the distal half of the fourth metacarpal bone ; (3) from the proximal part of the first 

 incision an opening may be made through the first interosseous space on to the dorsum, 

 care being taken to keep distal to the radial artery ; (4) a longitudinal incision between 

 the median and ulnar nerves, on the proximal side of the superficial palmar arch. At the 

 wrist a longitudinal incision may be made immediately to the ulnar side of the palmaris 

 longus tendon, thus falling between the lines of the median nerve and the ulnar artery. 

 To open the digital flexor sheaths, incisions are made along the middle of the palmar 

 surface of the fingers, opposite the first and second phalanges. The proper digital vessels 

 and nerves pass distally along the sides of the fingers, nearer the flexor than the 

 extensor surfaces. In cutting down upon the dorsal aspects of the phalanges, the incisions 

 should be made to one or other side of the extensor tendon, preferably upon the ulnar side, 

 to avoid division of the insertions of lumbrical muscles. The subcutaneous tissue of the 



