A A A. The _facial nerve_ emerging from underneath the ear, and distributing branches to the cheeks, temple, forehead, &c. This nerve excites the muscles of the face, and is chiefly instrumental in producing the expressions of the countenance under the changing emotions of the mind. B B B. _Muscles_ by which various motions are imparted to the head, face, mouth, &c., under the _stimulus of the nerves_. 960. _What are the nerves of sensation?_ The _nerves of sensation_ are those which _impart a consciousness to the brain_ that its commands to the nerves of motion have been obeyed, and how far they have been fulfilled. [Verse: "Oh that men would praise the Lord for his goodness, and for his wonderful works to the children of men."--PSALM CVII.] Let us perform a simple experiment, which will more clearly illustrate the phenomena of _motion_ and of _sensation_, which we are now describing, than a great deal of writing upon the subject. You hold in your hand this 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, _command_ 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 you 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 your 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 sensation 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.