THE BRACIIIAL PLEXUS. 755 



liy its posterior border, and corresponds inwardly to the vertebral artery and 

 vein, as well as to the nervous vertebral filament proceeding to tbe sympathetic, 

 suiil accompanying these vessels. 



Mode of distribution. Immediately after leaving the interspace in the 

 sealeims, the brachinl plexus arrives beneath the shoulder, near the scapulo- 

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

 which it is impossible to distinguish the terminal divisions and collateral 

 minuscules. Without noticing this distinction, however, we will describe 

 tin in in succession, commencing with those that pass to the trunk, and after- 

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

 in the following order : first, the shortest, 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 enumera- 

 tion : 



1. Diaphragmatic branches. 



2. Angularis and rhomboideal branch. 



3. Serratu* m<njnus or superior thoracic branch. 



4. Pectoral or inferior thoracic branches. 



5. Subcutaneous thoracic bram-li. 



6. Latissimus dorsi or great dorsal branch. 



7. Axillary nerve. 



8. Adductor brachii or teres major branches. 



9. Subscapular branches. 



10. Superscapular nerve. 



11. Anterior brachial or musculo-cutaneous nerve. 



12. Radial nerve. 



13. Ulnar or cubito-cutaneous nerve. 



14. Median or cubito-plantar nerve. 



PREPARATION OF THE BKACHIAL PjLExrs. The animal is placed in the first position, and 

 slightly inclined to one side by allowing one of the anterior limbs to hang mi- 

 ned. The pectoral muscles are tlien excised close to their insertion in the unfixed 

 limh, and turned upwards, maintaining them in this position by the chain tentacula 

 wliirh are detached superiorly to a hand that unites the extremities of the two 

 MI.-IH nxiry ili.ejonal bare. Care should be taken to separate the pcctoralis magnus from 

 .Hindi.-, in allowing the latter to fall on the table along with the limb. By tear- 

 ing through the considerable mass of cellular tissue surrounding the nerves of the 

 liiii' lii;il pi' xu-. these soon appear, and may be isobUcd with the greatest facility. It is 

 advisable in this dissection to preserve tli aiterie-t; and it is also of importance to 1< ave 

 the jM-rfoniting intercostal brandies intact, in order to observe the anastomoses of the-.- 

 with the subcutaneous thoracic division. 



In this o|M-r.ition. tin- anterior limh is very much sc]mnitcd from the trunk, and the 

 i.- of the nerves are necessarily more or less changed ; but it exhibits the whole of 

 the ph xii.- in the most perfect manner. 



To trace the divisions of the principal nerves from this pi- \n-. :i limb entirely 

 removed from the body is made use of, and, if possible, with the urteri. s injected. The 

 - :ire then found in their natur.d relations, and can IH- more mdilj di-.-i --t- !. 

 - 347, 318 will guide the student in looking for these nervous divisions. 



1. Diaphragmatic Branches. 

 See the description of the diaphragmatic nerve above. 



2. The Angularis and Rhomboideal Branch. (Fig. 347, 7.) 



Kntirely furnished by the sixth cervical pair, this branch is directed 

 upwards to the surface of the angularis (anterior portion of the serratus 



3 c 2 



