FUNCTIONS OF THE NERVOUS POWER. , 135 



been formed by one single bone ? I cannot possibly con- 

 ceive what is the use of so many little bones ; I should 

 think they would be very liable to be displaced amidst all 

 the motions, falls, and injuries that we are continually 

 experiencing in a greater or less degree. 



Dr. B. If the spinal column were formed of a sin- 

 le bone, the whole neck and body would be complete- 

 y stiff and unyielding admitting motion in no direction 

 whatever. In order to admit the various motions of 

 the body, some flexibility is necessary in the spine, and 

 this can be obtained only by forming it with a succes- 

 sion of several small bones, united together sufficiently 

 strong to allow the requisite degree of motion, without 

 at the same time endangering its strength. So firmly 

 are they united, that dislocations are the rarest of all in- 

 juries. 



Emily. My proposition was indeed absurd ; if I had 

 thought a moment longer I do'nt believe I should have 

 appeared so stupid. But knowing the names and anat- 

 omy of these parts, Dr. B., is of little use without a 

 knowledge of their functions. I suppose that anato- 

 mists who have examined the structure and develope- 

 ment of this system with so much perseverance, have 

 not neglected to investigate the uses of its several 

 parts. 



Dr. B. Certainly not ; a great degree of research 

 and ingenuity has been manifested in their investiga- 

 tions, and tney have been followed by some very inter- 

 esting results. The functions of the nervous system 

 have been reduced to two classes ; the nervous, and sen- 

 sorial, or they may be styled two distinct powers of 

 the nervous system. The nervous power is engaged in 

 the performance of vital, or organic actions ; the senso- 

 rial is the source of sensation, volition, intellect. 



The most important functions of the nervous power, 

 are those by which our relations with the external world 

 are maintained. Impressions made upon the organs of 

 sense, are transmitted by the nerves to the brain, and 



