518 LUMBAR NERVES. 



posterior just beyond the ganglion so as to form a single nerve 

 which almost immediately divides into an anterior and a pos- 

 terior branch, of which the anterior is the largest. 



The posterior branch proceeds backwards, and is distributed 

 to the muscles of the back. The anterior branch passes towards 

 the angle of the rib, in contact with the pleura. Soon after its 

 origin, this anterior branch ^ends off two ramifications which 

 unite to the intercostal nerve, at the ganglion ; it then proceeds 

 forwards with the blood-vessels, between the internal and ex- 

 ternal intercostal muscles, in the groove near the lower margin 

 of the ribs ; and terminates on the anterior part of the thorax. 

 In its course it sends branches, not only to the intercostal mus- 

 cles and pleura, but to the other muscles and the integuments of 

 the thorax. 



Some of the dorsal nerves differ from the others, as to the 

 ramifications which they send off. 



The first nerve, of this order, joins the lower cervical nerves 

 in the axillary plexus ; but it sends off the ramifications to the 

 sympathetic, and also a branch, which passes under the first rib 

 like the other dorsal nerves. 



The second nerve sends off a branch, which passes through 

 the external intercostal muscle into the axilla, and combines 

 there with the lesser internal cutaneous nerve, (or nerve of 

 Wrisberg) being distributed with it to the integuments of the 

 internal and posterior part of the arm. It is sometimes larger 

 than usual and supplies the place of the nerve of Wrisberg. 



The third dorsal nerve also sends off a cutaneous branch, 

 which is distributed to the axilla and the back part of the arm. 



These cutaneous branches of the second and third dorsal 

 nerves, are called Intercosto-humeral nerves. 



The lower dorsal nerves supply the muscles and integuments 

 of the abdomen. 



Of the Lumbar Nerves. 



There are five pairs of these nerves. The first of them 

 passes off between the first and second of the lumbar vertebrae, 

 and the others succeed regularly ; so that the last pair is situated 

 between the last lumbar vertebra and the sacrum. 



