Death, then, from the cerebral stimulants is usually an example of asphyxia. The heart, as in the same affection from other causes, continues to beat for a short time after respiration has ceased, sometimes in a greater or less degree for five minutes, thus affording the opportunity for the employment of recuperative measures, even after apparent death. Brodie first proved, by experiments on the lower animals, that, after apparent death from a narcotic poison, life might be saved by artificial respiration. The blood, being thus supplied with oxygen, begins again to move onward; and the heart, which has not yet quite ceased to beat, receiving a due supply, resumes its normal action, and the phenomena of life return. All that is necessary now is to continue the artificial respiration, until the nervous centres shall be in a condition to resume their function, and to support the strength of the patient against the secondary prostration. In several instances, these measures have been successful in the preservation of human life.
The cerebral stimulants are capable of producing their characteristic constitutional effects, to whatever part of the body they may be applied; a fact which strongly corroborates the idea of their operation through absorption. Of the ordinary avenues by which they are introduced into the system, with a view to remedial effect, they operate most speedily through the subcutaneous areolar tissue or lungs, next through the stomach, and after this through the rectum, or the skin deprived of the epidermis; and the duration of their effect is usually inversely proportionate to the rapidity with which it is induced.
The local effects of the cerebral stimulants upon the surface of application are analogous to their general effects, probably through their direct action upon the vessels and nerves of the part. They first excite the actions of the part, then diminish its sensibility, and lastly leave it, upon their removal, in a somewhat depressed condition; unless, indeed, their first stimulant impression shall have been sufficient to induce a positive inflammation, which will complicate the result.
This class of medicines, more rapidly than perhaps any other, lose their effect upon repetition. Each successive stimulant impression serves, in some degree, to lessen the excitability of the organs acted on; and, if time is not allowed for the system to recover its normal state before a renewal of the impression, this diminution of the excitability must be constantly and steadily continued. To produce a given effect, the dose of the medicine must be increased part passu with the diminution of the excitability; and there are no fixed limits within which this augmentation is restrained. As the medicines have no corrosive effect, and therefore do not directly destroy the organization of the parts on which they act, the quantity which an individual may attain the ability to support, with present impunity, is enormous. In Dr. Chapman's Therapeutics the case of a woman is mentioned, affected with cancer of the uterus, who took three pints of laudanum, besides a considerable quantity of opium daily, enough probably to kill from fifty to one hundred healthy individuals. (2d ed., ii. 236).
But the protracted use of the cerebral stimulants in excess is often attended with the most deplorable consequences in the end. As before explained, under the head of the Tonics, there are two great evils flowing from this abuse; the one, a gradual wearing out of the excitability of the system, and a consequent gradual depression of its functions and powers; the other, the production finally, in some one or more of the organs upon which the stimulant specially acts, of a low chronic inflammation, the result of the incessantly repeated irritation. This complication of general debility with local disease almost necessarily destroys life in the end, if it be not previously cut short by the occurrence of some accidental affection, which the exhausted frame is unable to support. More will be said on this point when the particular cerebral stimulants are treated of, which are most liable to be thus abused.
When the system has become habituated to one of these stimulants in great excess, its sudden withdrawal is sometimes followed by the most alarming prostration; and this is a fact which it is highly important to bear in mind, in the treatment of the diseases of individuals who are the victims of such self-indulgence. Even in their inflammatory affections, when depletion may be necessary to save life, though the habitual stimulant may be lessened, it should not be altogether withheld.