402 



TTTT: AXATOAfY OF TITE TTOP.SE 



ganglia 



controlling the organs of special sense, situated at the base of the 

 brain. Jth. The ccrebcllinn, which seems speci- 

 ally intended to conilnne and balance tlio several 

 muscular actions of the bod}-. 0th. The cerebrum, 

 whicli is the seat of intelligence and will. 6th. 

 The sympathetic system of ganglia, which speci- 

 ally controls the vital organs of circulation, diges- 

 tion, and depuration. The first five divisions are 

 generall}^ included under the head of the nervous 

 system of animal life, the last being considered 

 ttj be peculiar to organic life. The diagram on 

 the preceding page will show at one view the 

 chief comiioiu'ut parts nf the two systems. 



THE SPINAL CORD 



at 



The spinal conn ma}' be considered to be the 

 primary division of the nervous system, l)ecause 

 it represents the lowest development of this organ 

 in the animal kingdom. But instead of consist- 

 ing of a series of locomotive ganglia, as in the 

 (u-ticiduta, it is hei'e found in the shape of two 

 long masses of grey matter, covered with ■white 

 filjres, Avhich serve to communicate between the 

 several parts of which it is composed. 



Opposite each joint, between the vertebra?, a 

 nerve is given off, which passes out in the foramen 

 specially contrived for its exit, and thence goes 

 on to its destination. Each of these nerves has 

 two distinct origins ; one from the upper part of 

 the grey central matter (the sensitive root), the 

 other from its inferior surface, which is the motor 

 portion. The superior has an accession of grey 

 matter ai'ound it, soon after the union of its 

 nervelets, called its ganglion, beyond which the 

 two divisions unite to form a large nerve, wliich 

 soon begins to subdivide again for supplying the 

 several parts of the body. The terminating 

 branches reunite in loops, so that tliese nerves 

 may be consitlered to form a complete circle, 

 those of sensation receiving impressions from the 

 parts on which they are distributed, and conveying 

 them to the central ganglion, wliile the motor 

 nerves cause the muscles which they supply to 



tu:. S-2.— SriXAL Ccnp KEMovrp from its Canal. 



. n. Tioots of the sjiiiLil nrn'es. 



The filunieiits go'iig to unite to form each of the.se nen'c 

 Clear s]accs between the roots of the nerves. 



