3 o THE POPULAR SCIENCE MONTHLY. 



sat down with, pen, ink, and paper before me, but not a single 

 idea came into my bead, 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 prob- 

 ably 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 disagree- 

 able 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 called 



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. 



Fig. 12.— Tracing of the Rate of Circcla- 



tion m the Carotid. (After Marey.) A similar reason may be 



given to explain the habit of 

 snufling, 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 diffi- 

 culties 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 



