It is a noted fact that several of the most powerful substances are habitually received into the economy, even in formidable doses, apparently with no bad effect, at least with no immediate danger to life. The articles thus abused, for it is nothing else, are alcoholic drinks, tobacco, opium and other narcotics, and even arsenic and others.

It may be unnecessary to state that a person having the pernicious habit of taking any drug, to a high tolerance, is always a precarious subject for medication in any serious disease. The main reason is that any therapeutic habit will inflict an irreparable damage on the powers of absorption. When we take into consideration the exceedingly delicate processes some remedies undergo in their transition through the system before the absorbents receive them, and on their route to the different organs of election, their operative effects, and then their mysterious elimination, we know well, why longevity is denied to such, and why the blessings of medicine when sick does not rest on them!

What is the pathology of resisting an enormous dose of a dangerous substance by force of habit? The learned Gubler supposes that "it is an equilibrium established between the intensity of the action of a medicament, and the reaction of the system." This would make it a normal physiological operation, which surely is not the case. If the reaction of the system is equal to the intensity of the drug thus abused, how would we account for the progressive asthenic condition of the drunkard, and the opium eater, the longer they indulge in their habits?

It is a well-established fact that any medicinal substance of any power introduced into the system, not indicated as an absolute necessity does harm, and when such is persistently used, it will develop a cachexia eventually ending in an incurable organic disease.

The drunkard may die from cirrhosis of the liver or granular degeneration of the kidneys, the opium eater from general denutrition, the arsenic-eater from fatty degeneration, and the slave to tobacco from an early arrival of his disease of predisposition. But all hold alike a common functional malady in the first course of their habit. This being a blunted condition of the absorbents, which is soon transmitted to the nervous system, and finally establishes a functional cerebral lesion, known by the term

'craving." The degree of this brain trouble varies - in some cases it is curable, though usually not so. Hardly ever will a confirmed drunkard become radically reformed.

It is not owing to any extraordinary resistance of the system that gives tolerance of these noxious substances - but they have so worn out the powers of absorption for that particular kind of a substance, that its admission into the system is so slow and gradual, that no immediate serious consequence can follow, and when the substance finally finds its way into the circulation, further protection is rendered by the albuminoids as it is hurriedly carried to its assigned emunctories. The very weakness of the living tissues through which the substance passes facilitates its excretion exosmotically, on the principle that an indigestible ingesta may induce a diarrhoea.

Sometimes, changes in the system will take place where the absorbents have been aroused by some means, and should the victim at the time take the usual enormous dose of one of these substances he has been in the habit of taking, it may be with fatal results. It is not infrequently the case that the drunkard, and the opium, and the arsenic eater, are unexpectedly destroyed in this way.

A tolerance of medicine is not to be confounded with a tolerance brought about by a force of habit. Tetanus will bear an extraordinary tolerance of medicine, but the cause of this lies in the nature of the disease and the state of the absorbents, and not by any force of habit. All diseases bordering on collapse, bear the same tolerance and all from the same pathological cause.

It is well to keep in mind that a tolerance of medicine may be established when the same has been administered for a great length of time; this is in particular the case with laxatives and diuretics. When this takes place with a remedy in the treatment of a disease, the medicine may become nugatory as a curative agent, and should be abandoned. Therefore a judicious change in the course of a protracted treatment may be a necessity. The remedy may be resumed after the pathological toleration with its negative results has been overcome by recuperation, or by a special medical treatment.

However, there are many remedies, where there is no possible way to become habituated to them; as curare, prussic acid, tartar emetic, camphor, cantharides, some of the metals, and a large class of heterogeneous drugs of a high power, that chemically alone are incompatiable with the constituents of the human body.