THE LUMBAR NERVES. 751 



ascends towards the summit of the spinous processes of the dorsal 

 vertebrse, by passing between the semispinalis and longissimus dorsi; 

 the other is directed outwards, in traversing the substance of the latter muscle. 

 Inferior Branches. — These are more considerable in size than the 

 preceding, and descend into the intercostal spaces, between the pleura and 

 the internal intercostal muscles, or even in the texture of these. With the 

 exception of the first, whose arrangement is diiferent, they all pass at first 

 over the head of the posterior rib to reach the convex border of the anterior 

 one, and follow it to the extremity of the intercostal space. 



There they terminate in the following manner : those of the sternal 

 ribs traverse the pectoral muscles, giving filaments to these, and are 

 expended in the skin of the subthoracic region. Those of the asternal 

 ribs enter the abdominal muscles, passing between the transversalis and 

 rectus abdominis ; they also give cutaneous filaments to the skin of the belly. 

 Near their origin, the inferior branches communicate with the great 

 sympathetic, for the most part, by several filaments. 



In their course they furnish numerous fine ramuscules to the intercostal 

 muscles, and, in addition, give off, about the middle of their length, a very 

 thick division — the perforating intercostal branch, which traverses the costal 

 muscles and descends beneath the panniculus carnosus, ramifying partly in 

 that muscle and partly in the skin. The most anterior perforating branches 

 generally anastomose with the subcutaneous thoracic branch of the brachial 

 plexus. 



With regard to the first dorsal pair, its inferior branch enters the latter 

 plexus ; but it nevertheless furnishes an intercostal branch, always extremely 

 slender, which passes over the external intercostal muscle to be expended 

 in its substance before arriving at the sternum. The second pair also concurs 

 in the formation of the brachial plexus, though only by a small branch. 



Abticlb III. — Lumbar Nerves (6 Pairs). 

 Superior Branches.— Destined to the spinal muscles and the integu- 

 ments of the loins and croup, these are larger than the corresponding 

 branches of the dorsal region, and present an analogous disposition ; they- 

 give superior ramuscules to the muscles of the spine, and very long external 

 divisions which pass through these muscles to be distributed to the skin ot 



^ INFEMOR Branches.— The ^rsf, comprised in the interval separating the 

 last rib from the first lumbar transverse process, between the quadratus 

 lumborum and the psoas magnus, passes downwards and backwards until it gets 

 between the transverse and internal oblique muscles ot the abdomen, to which 

 it gives filaments, and is finally distributed in the great rectus muscle. 



Above the superior border of the internal oblique muscle, it furnishes a 

 perforating branch to the skin of the flank and the posterior part of the 



^'th^toXSosed in the same manner as the preceding, follows an 

 analogous course, and breaks up into several divisions which are lost m 

 the smaU oblique muscle. From one of these sometimes emanates a slender 

 filamrt which joins one of the inguinal nerves of the third pair. We 

 S not overlook, in the enumeration of the branches emitted by th,s 

 Scond pair of lumbar nerves, the two perforatng branches which descend 

 in front and on the inside, of the thigh, to be distributed to the skm of the 

 flank and the internal crural region. 



