After calling him by name, the brain wrote three pulsations which have the form of the preceding ones; then the pulse changed, and the pen traced four pulsations, one higher than the other. This is the beginning of what I have called an _undulation_. During the next pulsations the pulse-line gradually falls until it reaches the previous height. In comparing the form of the pulsations at the beginning of this curve with those at the end, we see that even this very slight emotion, which was not able to interrupt sleep, yet sufficed to produce a great modification. The pulse is stronger, its form tricuspid. We physiologists would say that, from being anacrotic, it had become catacrotic. But the variations which appear in the circulation of the brain during fear are far greater. The reproofs and threats which I uttered to Bertino when he was hindering my experiments by moving his head or hands, the disagreeable things which I sometimes purposely said to him, were always followed by very strong pulsations; the brain-pulse became six, seven times higher than before, the blood-vessels dilated, the brain swelled and palpitated with such violence that physiologists were astonished when they saw the reproductions of the curves, published in the tables of my researches on the circulation of the brain.[13] [13] _R. Accademia dei Lincei_, vol. v. series 3a; _Nuova Antologia_, March 1881. VII In Canada, in 1822, a soldier called Alexis St. Martin was shot at from a short distance. The bullet penetrated the abdomen, perforating the stomach. In a few months, thanks to the treatment of Dr. Beaumont, he was completely healed, only an opening remained in the abdominal walls through which the processes in the stomach could be seen. Several physiologists in America had thus the opportunity of observing the stomach during digestion by looking into its cavity as through a window. The investigations made on this soldier resulted in the statement that the stomach becomes redder as soon as digestion begins. Later, physiologists showed, by other observations, that the salivary glands grow red during mastication, and that the muscles contain more blood when they are at work a long time. We all know that the eyes of anyone who works long become red, that the feet swell after a long walk, and that, in fencing, the muscles of the arms and the hand which grasp the weapon grow thicker. From these facts we may deduce a law which has no exceptions, namely, that blood is more copiously supplied to an active organ.