Fig. 60.—MUSCLES OF THE HEAD AND FACE, WITH NERVES DISTRIBUTED THERETO.
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.
"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.