endowed with both the power of sensation and motion, is produced. There are thirty-one pairs of these compound nerves, the sensory and motor fibres of which are so commingled as to render it an impossible undertaking to separate them by any means at present known.
Now if, for instance, a needle be stuck into one of the fingers, the sensory fibres take the impression through the nerve and the posterior root to the spinal cord and thence to the brain. The command goes out to "draw the finger away." The mandate travels down the spinal cord to the anterior root, and thence through the motor fibres of the nerve to the muscles, which immediately act, and the finger is at once removed. All this takes place with great rapidity, but yet with nothing like the celerity once imagined. The researches of Helmholtz, a distinguished German physiologist, have shown with great exactitude the rate of speed with which the nervous fluid travels; and other observers, among whom Schelske deserves mention, have given a great deal of time and patience to this and kindred questions. As the result of many deliberations, it was ascertained that the nervous fluid moves at the rate of about 97.1 feet in a second. Now electricity travels with a speed exceeding 1,200,000,000 feet in a second, and light over 900,000,000. A shooting star moves with a velocity of 200,000 feet in a second, and the earth in its orbit around the sun, 100,000. A cannon ball has a mean velocity of 1,800 feet in a second; an eagle, 130; a locomotive, 95; and a race horse, 80. We thus perceive that the nervous fluid has no very remarkable rate of speed. A fact which, among many others, serves to indicate its non-identity with electricity.
Professor Bonders, of Utrecht, has recently been making some interesting experiments in regard to the rapidity of thought, which are likewise interesting. By means of two instruments which he calls the noëmatachograph and the noëmatachometer, he promises some important details. For the present, he announces that a simple idea requires the brain to act for .067 of a second for its elaboration. Doubtless the time required is not the same for all brains, and that by means of these instruments we may obtain definite indications relative to the mental calibre of our friends. What invaluable instruments they would be for nominating caucuses for vestries, for trustees of colleges, for merchants in want of bookkeepers; in short, for all having appointments of any kind to make!
For the eye to receive an impression requires .077 of a second, and for the ear to appreciate a sound, .149 of a second are necessary. The eye, therefore, acts with nearly twice the rapidity of the ear.
The sympathetic system yet remains to be described; but this is so extensive, and is so intimately connected with the well-being of the better half of creation, that policy and politeness require that it shall have a separate chapter to itself.
William A. Hammond, M.D.
