o50 NERVOUS SYSTEM. 



trunk, takes an oblique direction backward, and ramifies exten- 

 sively upon the aponeurosis of the external oblique muscle. 



The eighteenth and last intercostal nerve forms an exception to 

 this general description. It quits the last rib at its origin, and 

 stretches obliquely backward, passing close under the extremity 

 of the first lumbar transverse process. Soon after this it splits 

 into two branches ; the smaller one is directed backward across 

 the abdomen, passing at first between the external and internal 

 oblique muscles, but afterwards insinuating itself among the 

 fibres of the former, and ending in subcutaneous ramifications; 

 the larger one traverses the flank, and proceeds for a considerable 

 way between the internal oblique and transverse muscles. 



LUMBAR NERVES 



Correspond in number to that of the lumbar vertebrae. They 

 issue through the spinal foramina in the loins, and are, at their 

 exit, distinguishable into superior and inferior divisions. The 

 superior fasces, of minor importance, are reflected upward, and di- 

 rected into the mass of muscle forming the loin ; and, having dis- 

 tributed the majority of their branches therein, pierce the faschia 

 lumborum, and terminate in subcutaneous filaments. The infe- 

 rior divisions require to be distinctly considered. 



The first nerve runs obliquely across the transverse process of 

 the second vertebra, under the sacro-lumbalis, and at the end of 

 the third transverse process divides into two branches. The in- 

 ner one makes directly for the anterior spine of the hip-bone, over 

 which it passes, and disperses its ulterior filaments in an arbores- 

 cent manner upon the iliacus, covered by its faschia. The outer 

 branch takes a sweep outward, between the external and internal 

 oblique muscles, around the spine of the same bone, and extends 

 along the anterior border of the tensor vaginae netuly to the stifle, 

 and there ends in subcutaneous ramifications upon the faschia 

 lata. Its other branches are — 1. To the last dorsal nerve. 2. To 

 the sympathetic. 3. To the second lumbar nerve. 



The second nerve, though generally double from its origin, is 

 smaller than the first. It has communications with the first 

 nerve and sympathetic, and sends back a small branch that con- 

 tributes to the formation of the crural nerve. It also sends twigs 

 to the psoas. Its principal divisions are two. One is stretched 

 along the iliacus outwardly, and continues its passage along the 

 fore part of the haunch, where it becomes subcutaneous, and 

 ramifies over the stifle. The other division crosses the ilio-lum- 

 bar artery, just below its origin, and takes nearly a similar course 

 to the inward part of the haunch, where it disperses its ramifica- 

 tions upon the skin and faschia: in its way, it detaches a consi- 



