352 NERVOUS SYSTEM. 



The Jifth nerve runs backward, and plunges into the heads of 

 the coccygeal muscles. 



COCCYGEAL NERVES. 



Generally speaking, we find four pairs of them. Like the 

 sacral, they issue from the spine by two sets of foramina, and are 

 therefore best considered as divided into superior and inferior 

 sets. The sympathetic not extending thus far, they have no con- 

 nexion with it. In other respects they do not importantly differ 

 from the other spinal nerves. 



The superior fasces pass out obliquely backward ; commu- 

 nicate with the last of the sacral and with one another, distribute 

 many muscular branches, and end in subcutaneous filaments. 

 From the two or three last originates a considerable nervous 

 chord, which penetrates the erector coccygis, and may be traced 

 among its fibres to the extremity of the tail. 



The inferior fasces likewise communicate with one another. 

 The first nerve receives a branch from the last sacral, and de- 

 taches one to the perineum. Posteriorly, they all end in one 

 common nervous chord, somewhat larger than the one above, 

 which runs between the depressor and curvator coccygis, branch- 

 ing out in its course, and ending in filamentous ramifications at 

 the point of the dock. 



NERVES OF THE FORE EXTREMITY. 



With the exception of some cutaneous filaments ramifying 

 over the point of the shoulder and extending thence to the arm, 

 the fore extremity receives all its nerves (which are comparatively 

 large and numerous, not to add complicated) from the axillari/ 

 plexus; and this plexus is constituted, in a manner that has al- 

 ready been shewn, by a small branch from the fifth, by the prin- 

 cipal portions of the sixth and seventh cervical nerves, and by 

 the main division of the first dorsal nerve. The plexus, thus 

 formed, resolves itself into several large nervous trunks, generally 

 about seven or eight ; and these surround the axillary artery. 

 They are as follow : — 



The external thoracic nerves, commonly six or seven 

 in number, arise from the axillary plexus, and are disjDcrsed 

 upon the breast and side. Three or four of them run obliquely 

 downward, to give branches to the pectoral muscl,es. The others 

 take a backward course, and send branches to the serratus and 

 latissimus dorsi. One branch is found turning round the posterior 

 border of the triceps, where it becomes superficial and ramifies 

 among the fibres of the panniculus, extending thence into the skin. 



