Page:Popular Science Monthly Volume 42.djvu/40

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30
THE POPULAR SCIENCE MONTHLY.

sat down with, pen, ink, and paper before me, but not a single idea came into my head, not a single word could I write. Lying back, I soliloquized: "The brain is the same as it was yesterday, and it worked then; why will it not work to-day?" Then it occurred to me that the day before I was not so tired, and probably the circulation was a little brisker than to-day. I next thought of the various experiments on the connection between cerebral circulation and mental activity, and I concluded that if the blood would not come to the brain the best thing would be to bring the brain down to the blood. I laid my head flat upon the table, and at once my ideas began to flow and my pen began to run across the paper. I thought, "I am getting on so well, I may sit up now," but the moment I raised the head my mind became an utter blank, so I put my head down again flat upon the table and finished my article in that position.

Stimulation of some branch or other of the fifth nerve seems to increase the circulation in the brain, and those who are making their utmost calls upon their mental powers are accustomed to stimulate this nerve in one way or another. The late Lord Derby used to eat brandied cherries, and an experiment of Marey's (Fig. 12) proves that mastication will accelerate the flow of blood through the carotid artery, and serves to show the wisdom of an editor whom I knew who used to eat figs while writing a leading article, and even of those who indulge in the practice so disagreeable to their neighbors of chewing tobacco. Others stimulate the gustatory branches of the fifth nerve by the sweets which they suck, or by the smoke of a cigar or cigarette, while a rustic calledPSM V42 D040 Tracing the circulation rate of the carotid.jpgFig. 12.—Tracing of the Rate of Circulation in the Carotid. (After Marey.)upon suddenly to answer a question will probably excite the cutaneous branches of this nerve by scratching his head, and a man of more culture may stroke his mustache or beard, press his forehead or eyes, or, like many Germans, smite his nose with the forefinger.

A similar reason may be given to explain the habit of snuffing, formerly so much in vogue. The gentle titillation of the nasal mucous membrane by the snuff probably serves to stimulate the cerebral circulation, and the increased arterial tension due to the efforts of sneezing so increases the cerebral nutrition that difficulties seem at once to disappear, and obscurities of mental vision are so rapidly removed that snuff is said in popular language to "clear the head." The practice of snuffing has fallen to a great extent into disuse, but it may still be occasionally employed with