PERTURBATIONS OF SENSIBILITY.
Physical Pain.—The phenomena of sensibility, like all phenomena of vital activity, are susceptible of alternate lowering and exaltation, and of presenting maxima and minima of oscillation, in the interval between which their average periods are comprised.
Thus, when sensibility is locally annihilated, when the histological tissues are affected with a species of local torpor, anaesthetic phenomena present themselves. When, on the other hand, the contrary phenomena occur, when histological vitality rises several degrees to a state of cellular excitement, and the nervous elements reach a condition of continuous erethism—then manifestations of hyperwsthesia or pain occur. In these two cases phenomena connected with the natural sensibility of the nervous elements are always present, and, as it were, rise from zero to one hundred degrees.
The processes of anwsthesia and pain appear to develop like those of normal sensibility, independently of any nervous plexus which underlies them, from the simple fact of the existence of a cell capable of living and feeling.
It is certain, indeed, that in sensitive cells sensibility becohies obtuse and grows feeble under the influence of certain special conditions : chloroform makes their reaction impossible. Certain narcotic substances also appear to have a stupefying action on the sensibility of certain plants. It is certain again, that the sensibility of vegetables is perverted when they are thwarted as regards their natural evolution, and do not find in the soil with which they are furnished conditions favourable to their physiological nutrition. It is certain that they suffer also, as it is popularly said, and that their sensitive tissues, which are impressionable by external agencies, have to contend against wounds or with enemies of all kinds belonging to the animal and vegetable kingdoms, which under the form of parasites, oYdium, phylloxera, etc., fasten upon them and attack them even in their roots, in the very sources of life, thus inflicting upon them the same calamities we may see raging among individuals of the animal kingdom.
Pain, from the very fact that it expresses a purely vital action inherent in every living cell, vegetable as well as animal, is therefore the physiological equivalent of the individual sensibility of that same cell in conflict with the surrounding medium which impresses it painfully. It exists wherever there is a cell capable of living and feeling, and independent of the existence of any nervous element. Between the simple histological irrit ability of any anatomical element whatever, which is the rudimentary form under which it presents itself at first, and the most exquisite expressions of sensibility in superior beings, there are merely infinite degrees of sensitive vibrations which mark its different modes.
Just as we see a metal rod placed in a blazing furnace grow hot by degrees, and in proportion as the undula tions of the caloric become more and more frequent, pass in succession through the shades of bright red, dark red, and white heat, and develop as it grows hot both heat and light ; so the living sensitive cells, in presence of the excitations which affect them, undergo progressive exaltation as regards their natural sensibility, arrive at a period of erethism, and with a certain number of vibrations disengage pain, as the phy siological expression of this sensibility super-heated to a white heat. This is so true—the phenomena of pain are so really an act of vital reaction, that not merely the awakening of sensibility but a certain ten sion of it, is its necessary condition. When the ntrvous plexus is torpid, anaesthetic, pain cannot be developed. Suffering is not a thing of the will—to suffer we must feel.
All physicians know what curious phenomena the skin of hysteric patients often presents in this respect. You may pinch them, prick them, apply burning sub stances to the surface of the body ; the patients feel nothing save the simple contact of the substances applied ; their sensitive plexuses, stricken with a species of torpor, are incapable of erection, becoming and disengaging pain.