So Boccaccio describes the diagnosis of the illness of the Count of Antwerp; and long before Boccaccio, Plutarch had already stated that the physician Erasistratus discovered the love of Antiochus to Stratonice from the tumultuous irregularity of his pulse.
We here touch upon one of the greatest problems which criminal science will propound in the future, when it asks the physiologist: 'Tell us of what does this man think, who remains impassive before the traces of his crime? Tell us if within him there is nothing pulsating—nothing, either human or animal?'
Fig. 3.—Curve showing Cardiac Pulsations of a Quiet Dog
I have in my laboratory a dog which was of service to me in a few studies on fatigue. He is such a good animal that for two years I have kept him, together with two other dogs of which I have grown fond, and which, like old friends, shall always stay with me, unless some dog-lover comes to beg them from me, as so often happens with good, faithful dogs, that only in the physiological laboratories can escape from the certain and cruel death to which the Corporation condemns them. As he is a quiet dog, it occurred to me one day to try the effect of a violent noise upon him. I made use of a little instrument called a cardiograph, because it transmits the heart-beats to a lever which traces them on a cylinder covered with smoked paper. I applied this instrument, which is about the size of a half-crown, on the place where the heart beats between the ribs, fixing it by means of an elastic band fastened round the thorax. At first it wrote the curve of the cardiac pulsations represented in fig. 3, which is reproduced by means of photozincography. I regret having to present the reader with more curves, but when one is able to see what the heart itself writes, it would be unpardonable to try to translate its characteristic language into words. Besides, it is not difficult to understand these curves. The line T signifies the time; it is written by an electric clock which raises a pen every second and marks a tooth. It is, so to speak, a controlling line, indispensable in graphic studies by which one wishes to learn with the greatest exactness the changes which the frequency of the pulse undergoes. In the line T eighteen seconds are marked, and the heart-beats registered in the same time in line A amount to twenty-nine. If I had applied the cardiograph to the thorax of a man I should have obtained a similar curve with fewer pulsations. At each beat of the heart the pen rises and falls rapidly, and then writes below a trembling line during which the heart does not beat. As the thorax rises and expands during inspiration, the pen resting on the ribs must likewise rise, therefore the three or four pulsations taking place during the expansion of the thorax are marked successively higher, sinking again with the commencement of expiration, thus forming waves, as it were. From this curve, traced while the animal was tranquil, we see that its heart, as indeed is also the case in man, beats more frequently during inspiration than during expiration, the heart-beats being nearer to each other in the ascending portion of the curve, and further apart in the lower portion which corresponds to the end of each expiration.
While the animal was perfectly quiet I motioned to my servant to fire a gun, but he failed. It was an old hunting-gun, badly loaded perhaps, and only the cartridge had caught fire. The dog, however, at once tried to rise, and became strangely excited, much to our surprise. I had my hands on the instrument which lay on the ribs where the heart beats, and felt that its palpitations had become stronger and more rapid. About a minute later we succeeded in taking the curve B in fig. 4, from which may be seen how much more frequent the pulsations were. The animal had become so restless that we had to give up the experiment and set him at liberty. When he was on the ground he went round the laboratory sniffing everywhere. Presently we took the curve C, fig. 4, from which we can see that the emotion was not yet over, since the beating of the heart is still quicker than in the normal curve marked in fig. 3.
Fig. 4.—Cardiac Pulsation during Emotion
There were several of us together when this experiment was made—the students of the laboratory, my assistants, and Professor Corona, and we were all astonished at what took place. Some of the bystanders said at once that it must be a hound. We had always taken him for a watch-dog, as he was very big, and did not look in the least like a hound. We determined to try a decisive experiment the next day.