230 THE BEASON WHY. 



" Oh that men would praise the Lord for his goodness, and for his wonderful 

 works to the children of men." PSALM cvn. 



Let us perform a simple experiment, which will more clearly illustrate the 

 phenomena of motion and of sensation, which we are now describing, than 

 * great deal of writing upon the subject. You hold in your hand thisi book : 

 close it, and set it upon the table ; lay your hands passively upon your lap, 

 and then will your hand, to take up the book, which is the same as to say, com- 

 mand your hand to take up the book. What occurs ?^ The hand, immediately 

 obeying your desire, stretches forward to the book, and takes hold of it. How 

 do you know that you have hold of it ? You see that yon have : but were your 

 eyes closed, you would be equally aware that the hand had reached the book, 

 and fulfilled your wishes. It is by the nerves of sensation that you are made 

 aware that the hand has fulfilled yoxir instructions. 



Consider what took place in the simple action. In the first instance, a 

 desire arose in your mind to take up the book. The brain is the organ of the 

 mind ; and having branches either proceeding from itself, or from the spinal 

 cord, to every part of the body branches that traverse like telegraphic wires 

 throughout every part of the system, it transmitted instructions along the 

 nerves that proceed to the muscles of the arm and hand, directing them to take 

 up the book. This was done instantly ; and as soon as it was done you became 

 conscious that your will had been obeyed because the nerves sent back a sen- 

 sation to the brain acquainting it that the book had been taken up, and that at 

 the moment of the dispatch it was in the firm hold of the hand. 



In all the varied motions of the body this double action of the nerves takes 

 place. It is obvious that without an outward impulse from the brain, upon 

 which the desire of the mind first made an impression, no motion of the mus- 

 cles of the arm and the hand could have taken place ; and it is also obvious that 

 without an inward impulse from the nerves to the brain, you would not have 

 known that the muscles had fulfilled your instructions. The hand might have 

 dropped by the side of the bock, or have gone too far, or not far enough, and you 

 would not have been waare of the result, but for an inward communication 

 through the nervs. 



We are not now speaking of the nerves which endow us with the sense of 

 feeling ; because they are regarded as separate and distinct from those nerves 

 that produce in us consciousness of muscular response. When we walk, rise, or 

 sit, we are made conscious, without any special feeling being exerted, that the 

 muscles have placed the limb, or the body, in the desired position, that it is 

 set down safely and firmly, and that we may repose upon it securely without 

 further attention. We refer the impressions made by the book upon the nerves 

 of the hand, and which enable us to tell whether it feels hot or cold, 

 whether its surface is rough or smooth, and so on, to the special sense of feeling. 

 The consciousness of muscular action is a separate and distinct function ; and 

 it is generally believed that the same nerves that convey the command of the 

 will outward, bringing back the intimation that the will has been obeyed, but 

 that different fibres of the nerves convey the outward and the inward impulses. 

 A single nerve may therefore be ,'ikened to a double wire connected with the 

 electric telegraph: one transmittii 'g despatches in one direction, and the other 

 iu the opposite direction. 



961. What are the nerves of special sense ? 

 The nerves of specisJ. sensj an those thrcugrh which we hear,se0t 

 feel, smell, and taste. 



