Page:Popular Science Monthly Volume 17.djvu/322

308 a visit." I have translated as literally as possible Mosso's words—those unfamiliar with Italian should remember that words like "veneration" and "master," when rendered literally, convey a more fervid feeling in English than is expressed by the original. We reproduce the tracing referred to; the upper line is drawn by the pen, and its descent corresponds to the diminution of the volume of Mosso's right forearm; A marks the point when Professor Ludwig entered. The lower line records the time, each notch corresponding to an interval of five seconds. The diminution of volume was equal to about six



cubic centimetres. This effect was not due to any strong emotion of fear or anxiety, but merely to the affectionate respect which Professor Ludwig's genial manners win from his pupils. The same experiment was tried upon Dr. Pagliani, with the same result.

Cerebral activity, like all the emotions, is reflected by the vascular system. To test this, the person experimented upon was given some simple arithmetical problem to solve; this was chosen because it could be solved without the person's speaking, which would have necessitated a change in the respiration, and so have modified the circulation. Fig. 3 shows the effect of calculating 245 X 15. The lines as before. This experiment was made upon Dr. Frey, and testifies to the great effect of a comparatively light and brief mental labor. It appeared that the



more complicated the sum to be solved the longer and greater was the contraction of the arm. The response of the circulation is very ready and marked, and, in persons of excitable temperaments, strong effects are produced from such very slight causes that it is sometimes difficult to make any experiments upon them.

There is undoubtedly a relation between the intensity of the