SCO 



THE NERVES. 



Even before its arrival at the tendinous centre, tliis nerve divides into 

 several branches, the ramifications of which pass to the sides of the crura of the 

 diaphragm. 



Brachial Plexus. 



This plexus comprises an enormous fasciculus of nerves, situated between 

 the thoracic parietes and the iimer face of the anterior Limb, formed by the 

 inferior branches of the sixth, seventh, and eighth cervical, and the two first 

 dorsal pairs ; they are principally sent to the muscles and integuments of that 

 limb. 



Mode of constitution. — The sixth cervical pair only assists in the formation 

 of this plexus, by the slender filament from its diaphragmatic branch ; but the 

 next two are entirely devoted to it, as well as the first dorsal, with the exception 

 of a very thin ramuscule, which constitutes the first intercostal nerve. The root 

 furnished by the second dorsal pair only represents a very small part of its 

 inferior branch, the other portion forming a somewhat voluminous intercostal 

 nerve. 



The various branches converge towards each other, and gain the space 

 between the two portions of the scalenus muscle (if we consider it as one), where 

 they unite, and become confounded into a single fasciculus by sending filaments 

 and ramuscules to each other ; this fasciculus soon separates into a certain 

 number of divisions, the disposition of which will be referred to presently. It 

 will be remarked that the intercrossing of the branches composing the brachial 

 plexus does not occur in a confused and irregular fashion, and if the reticulation 

 of the ramuscules passing from one to another does not take place in a constant 

 manner, it is, at any rate, far from being inextricable. It is easy to follow the 

 filaments from any pair of nerves for a certain distance in the divisions given 

 oif by the brachial plexus, especially after maceration in dilute nitric acid. This 

 originating fasciculus of the brachial plexus is very wide and short. It is at 

 first comprised between the superior portion of the scalenus (or superior scalenus) 

 and the longus colh. In its course between the two portions of that muscle, 

 it bends round the first rib by its posterior border, and is related inwardly to the 

 veitebral artery and vein, as well as to tlie vertebral nerve-filament proceeding 

 to the sympathetic, and accompanying these vessels. 



Mode of distribution. — Immediately after leaving the interspace in the 

 scalenus, the brachial plexus arrives beneath the shoulder, near the scapulo- 

 humeral angle. There it divides into a certain number of branches, amongst 

 which it is impossible to distinguish the terminal divisions and collateral 

 ramuscules. Without noticing this distinction, however, we will describe them 

 in succession, commencing with those that pass to the trunk, and afterwards 

 those which are destined for the limb. The latter will be examined in the 

 following order : first, the shortest branches, or those which proceed to the 

 upper parts of the member ; and next, the longest branches, or those passing 

 to the foot. 



All these divisions are named and classified in the following enumeration : — 



