Chap. XL] THE BRAIN AND NEltVES. 225 



the muscles of the shoulder dorsal to the head of the humerus ; 



a median (m.) 9 which passes 



to the radial side of the fore- 



arm; an ulnar (w.), which c . v . | 



passes to the ulnar side of the 



fore-arm : and a musculo-spiral Jy vnl i 



* LIL. I. T 



(m. s.), which dives to the 



dorsal side of the humerUS, FIG. 72. BBACHIAL PLEXUS RABBIT. 



and then passes to the radial c . v.-c. viii. Fifth to eighth cervical nerves. 



side of the fore-arm. The ** * First thoracic nerve, c/. circumflex 



nerve, m. Median nerve, m. s. Musculo-spiral 

 Other thoracic nerves run nerve, ul. Ulnar nerve. 



out between the ribs. In 



the rabbit the lumbo-sacral plexus is formed by the union 



of the fifth to the seventh lumbar and first to the third sacral 



nerves. It gives rise to a crural nerve to the front of the 



thigh, an obturator nerve to the muscles near the acetabulum, 



and a great sciatic passing out between the ischium and the 



sacrum. 



In the pigeon there is a brachial plexus which supplies the 

 wing ; a lumbar plexus, giving off the larger femoral nerve over 

 the front edge of the ilium to the front of the thigh and the 

 obturator nerve through the obturator fissure to the muscles 

 near the acetabulum; and a sciatic plexus giving rise to the 

 sciatic nerve which passes through the ilio-sacral foramen. 



The Sympathetic System. In the frog the sympathetic system 

 has ten or more ganglia on either side, connected by longitudinal 

 connectives These lie within the subvertebral lymph-space, and 

 posteriorly are closely connected with the aorta. Each ganglion 

 receives a filament from a spinal nerve. The most anterior 

 ganglia are united by filaments with the ganglion of the ninth 

 and tenth cranial nerves, from which a delicate thread passes 

 into the cranial cavity and unites with the Gasserian ganglion. 

 Branches of the sympathetic accompany the blood-vessels, a 

 large splanchnic branch (on which is developed a cceliac ganglion) 

 passing along the coeliaco-mesenteric artery. 



In the rabbit the sympathetic may be seen in the thoracic 

 15 



