NEUROLOGY. 135 



PI. 138, fig. 4, brachial plexus unravelled : '■ ''j fifth and sixth cervical 

 nerves ; ', branch arising from the union of the two and dividing into \ the 

 musculo-cutaneous nerve, and \ a connecting branch of the median nerve ; 

 "' ', eighth cervical and first dorsal nerve ; *, their connexion, and °, their 

 division into a branch going to the median nerve, the ulnar nerve '", and 

 the internal cutaneous nerve " ; "', small internal cutaneous nerve ; "', median 

 nerve; "■'', radial, nerve; ", posterior thoracic. Fig. 6, relations of the 

 digital nerves or the palmar side : '■ ', digital nerves ; ", plexus at the tip of 

 the finger formed by the union of the two. Fig. 7, relations of the digital 

 nerves or the dorsal surface : '' ', dorsal nerves ; '•'' "^^ branch of the preceding 

 nerves passing round to the dorsal surface. 



4. The Dorsal Nerves are twelve in number on each side. The first 

 pair passes between the two first dorsal vertebras, the last pair between the 

 last dorsal and first lumbar vertebrae ; the first is very large, the following 

 diminish in size, but the two last again increase, and the twelfth is nearly 

 equal to the first. These nerves are distributed to the parietes of the 

 thorax and abdomen, also to the muscles and integuments on the posterior 

 and lateral regions of the trunk ; they are not connected together in any 

 plexus like the cervical, lumbar, and sacral nerves, but are distributed 

 separately. All their anterior branches, however, are united through the 

 medium of the chain of the dorsal sympathetic ganglions, each of the former 

 being connected by one or two filaments to one of the latter ; the first 

 dorsal also joins to the last cervical in the brachial plexus, and the last 

 dorsal is connected to the first lumbar ; they all divide into a posterior and 

 an anterior or intercostal branch. The posterior or dorsal branches are 

 smaller than the anterior ; they each pass backwards, accompanied by the 

 posterior branch of the intercostal artery, through a foramen formed above 

 and below by the spinous processes, internally by the bodies of two verte- 

 brae, and externally by the anterior or great costo-transverse ligament ; 

 they supply the muscles and integuments of the back and loins. 



The anterior dorsal nerves, excepting the first, are named the intercostals, 

 and pass round the parietes of the thorax between the laminae of the inter- 

 costal muscles, and inferior to the intercostal blood-vessels : the superior 

 five or six are confined to the chest, and extend as far as the sternum ; the 

 anterior portions of the inferior five or six are placed in parallel lines 

 between the abdominal muscles, and extend to the rectus. They supply 

 the parietes, muscles, and integuments of the thorax and of the upper part 

 of the abdomen. 



5. The Lumbar Nerves. There are five pairs. They are larger than 

 the dorsal, and increase in size downwards ; the first escapes between the 

 two first lumbar vertebra?, the fifth between the last vertebrae and the 

 sacrum ; like the dorsal, they divide into posterior and anterior branches. 

 The posterior pass between the transverse processes to the lumbo-spinal 

 muscles, and each divides close to the multifidus spinse into an internal and 

 external branch ; the former is lost in the multifidus spinae, inter-spinous, 

 and inter-transverse muscles; the external branch is large and musculo- 

 cutaneous, supplying the sacro-lumbalis and lumbar aponeurosis. The two 



841 



