What is the last expression of pain, the last manifestation of sensibility? This is a question we must study in order to learn the relative importance of the phenomena making up the picture of fear, and to see which of these offer the most lengthened resistance in the struggle with death.
By means of chloral or alcohol I have produced such a profound sleep in dogs or rabbits that they could not rouse themselves again. One cannot imagine a quieter decease, a gentler and more gradual sinking of the organism into the arms of death.
As soon as a strong dose of chloral or alcohol has been administered, the animal becomes somewhat excited, the hind legs begin to give way; when we call him he cannot turn without falling; he rises, makes another attempt, totters, turns round, falls again, rises with difficulty, and finally lies down stretched out and tranquil. From time to time he tries to raise his head and then falls into a leaden sleep. The respiration is slower, the temperature gradually falls, at length the wagging of the tail ceases. The lids droop over the sleepy eyes, the face is tranquil, the ears motionless, whatever pain the efforts made to awaken him may cause. One might think he was dead.
The only method which physiologists had of finding out whether an animal in this condition was still capable of feeling was by investigating whether the heart and blood-vessels still responded to painful stimuli.
My friend, Professor Foà, showed in a work carried out together with Professor M. Schiff,[14] that even when heart and blood-vessels no longer respond, when the circulation is no longer modified, whatever may be the perturbation of the nerve-centres, a last trace of sensibility may still be observed in the eye, the pupil dilating whenever the animal is irritated.
But I have seen dogs, poisoned with chloral, of which the temperature had sunk to 30°, so extremely slow had the chemical processes of respiration become; no electric current, no mechanical action was capable of producing even the slightest movement of the limbs or face; the pulse, pressure of blood, the pupil, in a word everything had become impassive, no effect being obtained on the pulse even when the cardiac nerves were laid bare, severed, irritated by electric currents—and yet the animal was still sensible. By carefully studying the respiration I saw that it was modified whenever a leg or any other part of the body was pinched.
The alteration of the breathing is therefore the last function of the organism in which sensibility and emotion reveal themselves.
V
We know that, whatever nerve of the skin is irritated, a succession of deeper and more frequent inspirations follows, and we have seen that this phenomenon is useful to the organism. But if the excitement of a nerve becomes so strong as to cause violent pain, or if a very vivid impression is received as in fright, the mechanism stops short midway in a deep inspiration, and this is injurious.
Some few times I have been in danger of my life, and always remember to have felt a terrible oppression, as though my breath had been cut short. A few months ago I was overtaken by a storm on the mountains, when the lightning struck the ground about fifty steps from me, and I remember having noticed that respiration was arrested for several seconds.