198 



THE NERVOUS SYSTEM. 



The third ganglion {Ga/t(/ lion canUacnm hamle, Gaskell andGadow) 

 is sometimes fused with the second, but is usually close to the third 

 spinal nerve : it has a short but distinct Emnus commuyiicans. 



Behind the third gang-lion the sympathetic cord is continued back- 

 wards along the corresponding aortic arch, then parallel with and 

 close to the abdominal aorta (Figs. 117, 127, and 131), receiving 



Bami communicantes^ which are 

 long and well marked, from 

 each of the spinal nerves ; 

 the fourth, fifth, and sixth 

 nerves usually supply each 

 one Rannis communicans, the 

 seventh two, and the eighth 

 and ninth each two or three : 

 from the tenth nerve it re- 

 ceives three or more, as manj^ 

 as twelve having been noted. 

 The ganglia are usually more 

 or less spindle-shaped or flat- 

 tened and triangular; the 

 hinder part of the cord usually 

 receives in addition two or 

 three branches from the sciatic 

 plexus and twigs from the 

 R. aMominalis of the N. 

 coccygeus. 



The branches and commu- 

 nications of the sympathetic 

 cords are as follows : — 



a. Communicating branches 

 between the two cords : these 



Sympathetic cord. Fiom Ecker (Icônes physiologicae, 



PI. XXIV, Fig. 3). 



The heart, lungs, and livev have been removed ; the 



stomach, intestine, kidneys, and testes drawn to the 



right side ; the left sympathetic cord is thus pulied 



to the right side to expose the Rami communicantes. 



S Sympathetic cord attached to the ganglion of the are CxtrCmcly numerOUS and 



^^^^- irregular, forming a net-like 



The numbers refer to the gangha, which are enumer- . 



ated from before backwards. plcXUS, whicll SUrrOUuds the 



abdominal aorta and other adjacent structures, and gives off 

 numerous small twigs to the neighbouring vessels and organs. 



b. Communications with the cranial nerves ; these are two 

 branches (Wiedersheim), (Figs, m and 116) which pass from the 

 first ganglion to the Ganglion nervi vagi, where one terminates, the 

 other leaves the ganglion to pass on to the Gasserian ganglion 



