THE BKAlD. 



57 



pleasurable or painful sensations. One of them is spread over 

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

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

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

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

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

 bestows the power of feeling. 



One division of nerves {h, Fig. 3), springing from a prolonga- 

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

 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 in- 

 voluntary motion ; so that, whether he is awake or asleep, con- 

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

 irom 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 lie very tip of the tail — other nerves are 

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

 of them. The spinal cord a, is combined of six diitinot coluinufl 



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

 The two upper columns — the portion of spinal marrow represent 

 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 inner 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. 

 Beyond the ganglion the two unite, and form a perfect spinoi 



