NERVOUS POWER. 323 



merable branches to be distributed all over the 

 body. All the parts receiving blood-vessels, and 

 more especially the organs of digestion, are abun- 

 dantly supplied with ganglionic nerves ; so that, 

 by their intervention, all these parts have extensive 

 connexions with the brain and spinal cord, and 

 also with one another. A great portion of the spinal 

 cord itself may also be considered as performing 

 the functions I have here assigned to the ganglia, 

 and consequently as forming part of the ganglionic 

 system : for although it differs much from the 

 ganglia in form and appearance, yet it is found to 

 correspond with them in all the essential charac- 

 ters of its structure, being composed of a mass of 

 grey neurine, at which white nervous filaments 

 either arise or terminate. These filaments, like 

 those of the ganglia, may be regarded, according 

 to their functions, as either afferent or efferent ;* 

 the former serving to convey impressions from the 

 remote extremity of the filament to the central grey 

 neurine, and the latter to transfer from thence a 

 corresponding impression to other parts. All this 

 may be done without participation of the brain, or 

 of any other part of the nervous system ; and with- 

 out the occurrence of sensation, volition or any other 

 mental affection. The numerous communications 

 and interchanges of filaments, which subsequently 

 take place at various parts, forming what is called 

 a plexus, are shown in Fig. 380 : where four trunks 

 (t, t) divide into branches, which are again sepa- 



* Dr. Marshall Hall, who is the author of this distinction, has 

 termed these two classes of fibres, respectively, the incident and the 

 reflex nerves : and the whole system, comprehending the spinal 

 cord and ganglia, performing the above mentioned functions, he 

 terms the excito-motory system. 



