THE L;RA1^. 



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pleasurable or painful sensations. One of them is spread over 

 the membrane of the nose, and gives the sense of smell ; another 

 expands on the back of the eye, and the faculty oi' sight is gained ; 

 and a third goes to the internal structure of the ear, and tlie ani- 

 mal is conscious of sound. Other nerves, proceeding to ditierent 

 parts, give the faculty of motion, while an equally important one 

 bestows the power of feeling. 



One division of nerves [Jl, Fig. 3), springing from a prolonga- 

 tion of the brain, and yet within the skull, wanders to difierent 

 parts of the frame, for important purposes connected with respira- 

 tion or breathing. The act of breathing is essential to life, and 

 were it to cease, the animal would die. These are nerves of ^?^- 

 volic?itary motion ; so that, whether he is awake or asleep, con- 

 scious of it or not, the lungs heave and liie is supported. Lastly, 

 from the spinal cord q — a farther prolongation of the brain, and 

 running through a cavity in the bones of the neck, back, and 

 loins, and extending to the very tip of the tail — other nerves are 

 given off at certain intervals. The cut below delineates a pair 

 of them. The spmal cord a, is combined of six dii^tinct columns 



Fia:. 6. 



or rods, running through its whole length — three on either side 

 The two upper columns — the portion of spinal marroAV represeu' 

 ed in our cut, is supposed to be placed with its inner or lower 

 surface towards us — proceed from those tracks of the brain devoted 

 to sensation. Numerous distinct fibres spring abruptly from the 

 column, and which collect together, and, passing through a little 

 ganglion or enlargement, d — an enlargement of a nervous cord is 

 called a ganglion — become a nerve of sensation. From the 

 lower or imier side, — a prolongation of the track devoted to 

 motion, — proceed other fibres, which also collect gradually to- 

 gether, and form a nervous cord, c, giving the power of motion. 

 Reyond the ganglion the two unite, and form a perfect spinal 



c 



