FOREARM AND HAND 97 



It should be noted that, except in the case of the thumb 

 and little finger, the dorsal collateral nerves do not reach the 

 extremities of the digits. The skin on the dorsum of the second 

 and third phalanges of the digits is chiefly supplied by twigs 

 which proceed backwards, from the palmar collateral branches 

 of the median and ulnar nerves. As already stated, it is 

 from the branch of the superficial division of the radial nerve, 

 which goes to the lateral side of the thumb, that the radial 

 palmar cutaneous nerve arises. 



Numerous fine filaments are given to the skin on the 

 dorsum of the hand, and a certain amount of crossing of the 

 adjacent ulnar and radial twigs takes place in this locality ; 

 in other words, twigs from the one nerve invade the territory 

 which is occupied by the other nerve. 



Fascia Antibrachii (Fascia of the Forearm). The deep 

 fascia which envelops the forearm should now be cleaned by 

 removing the subcutaneous adipose tissue. It is an apon- 

 eurosis of great strength and density. More particularly 

 is this the case on the dorsal aspect of the limb, and also 

 in the distal third of the forearm, where the fleshy bellies of 

 the subjacent muscles give place to the tendons. In its 

 proximal part it receives an accession of fibres from the 

 tendon of the biceps brachii in the form of the lacertus 

 fibrosus. Some fibres are also given to it by the tendon of 

 the triceps. Near the elbow it serves as a surface of origin 

 for the numerous muscles which spring from the epicondyles 

 of the humerus, and from its deep aspect dense septa pass 

 between the fleshy bellies. These partitions are indicated on 

 the surface by a series of white lines. At the wrist it becomes 

 continuous in front with the lig. carpi volare and the tig. carpi 

 transversum (O.T. ant. annular lig.), whilst behind it forms an 

 obliquely placed, thickened band, the lig. carpi dorsale (post, 

 annular lig.). On the dorsum of the hand the deep fascia is 

 thin. 



VOLAR SURFACE AND MEDIAL BORDER OF THE FOREARM. 



In this dissection the following structures will be brought 

 under the notice of the student : 



1. The radial and ulnar arteries and their branches. 



2. The median and ulnar nerves and their branches. 



3. The ramus profundus (O.T. posterior interosseous) and the ramus super - 



ficialis of the n. radialis. 



4. The group of pronator and flexor muscles. 



VOL. I 7 



