NERVOUS SYSTEiAJ. 3^19 



The superior hraitc/ies turn directly upward between the trans- 

 verse processes, piercing the intercostal muscles and mounting 

 upon the back, where they proceed obliquely upward, deeply 

 buried in muscle, until at length they grow very small, and be- 

 come superficial, and end in subcutaneous ramifications upon the 

 faschia of the back. 



The dorsal nerves grow smaller accordingly as they are given 

 off more posteriorly. The anterior divisions of them furnish 

 branches to the muscles of the dorso-scapular region ; the mid- 

 dle and posterior, to the muscles of the dorsal region : the hinder 

 nerves also send a few filaments to the loins. 



The intercostal nerves require that we enter farther 

 into particulars. 



The Jirst nerve is of large size, and its principal portion is 

 destined to the humeral plexus. The proper intercostal nerve is 

 but a slender branch. It is remarkable for its solitary course: 

 the other intercostals, for the most part, accompany the inter- 

 costal vessels, v.hereas this maintains a middle course between 

 the first and second ribs, and ramifies upon their lower extremi- 

 ties. It is also distinguishable from all others but the second, in 

 not furnishing any cutaneous ramification. 



The second nerve detaches, near its origin, a considerable 

 branch, which describes an arch downward in its course over the 

 belly of the longus colli, and afterwards joins the first nerve. Its 

 intercostal branch, which is rather larger than the first intercos- 

 tal nerve, runs for some distance along the muscular space, and 

 then accompanies the intercostal bloodvessels, and, like the first, 

 ends in ramifications near the sternum. 



The third, fourth, Jijlh, sixth, and seventh intercostal nerves, 

 furnish, each of them, a long cutaneous filament which ramifies 

 among those muscles of the costal region exterior to the ribs; 

 they then pursue their course downward, incline forward be- 

 tween the cartilages, and expend their ulterior ramifications 

 among the muscles of the sternal region. 



The remaining intercostal nerves, with the exception of the 

 last, having reached the lower ends of the ribs, do not continue 

 their course between the cartilages, but quit the intercostal 

 spaces and traverse the under surfaces of the cartilages, to reach 

 the muscular parietes of the abdomen, where we find them pur- 

 suing their way in parallel lines, nearly at equal distances from 

 one another, between the transverse and internal oblique mus- 

 cles, to the rectus, in the substance of which they branch out and 

 are lost. From the thirteenth nerve, and from every one poste- 

 rior to it, before they leave the intercostal spaces, issues a large 

 cutaneous brand), which, deviating i'rom the continuation of the 



