In reply I would say that any poisonous or unnatural substance ingested into the living body, in amount within the ability of the vital organism to _readily_ expel it; or even of the most wholesome food substance in excess of the _needs_ of the organism, and yet, again, not so excessive as to depress the vital forces instead of spurring them to increased efforts to thrust it out, is a stimulant. In short, anything of an injurious nature, by reason of quality, amount, or the conditions under which it is administered, may produce stimulating effects. But the inevitable “reaction” of stimulation is depression; although, from natural causes, convalescents often make sufficient progress to overwhelm, or at least obscure, the evidence of the secondary effects. Speaking with direct reference to the effect of alkaloids in general, Professor Prescott says, “While a certain portion stimulates the nervous system, a large portion acts as a sedative, so that a difference in quantity of the potion causes a difference in kind of its effects.” It should ever be borne in mind that the increased action under stimulation is simply the extra effort forced upon the vital organism to expel an intruder——the intruder being the stimulant itself. If this be the case, it necessarily follows that stimulants deplete, and can never replenish the vital exchequer. Instances have been noted of children who were observed to be unusually active and jubilant immediately prior to an “attack” of diphtheria. In such case——and a true history of every case might establish this as the rule——the diphtheritic poison acts as a stimulant; nature is trying to thrust it out, and all the life forces are abnormally active. We can not know in how many instances she succeeds in these efforts, nor yet how often her defeats are due to the administration of poisons, and food that for want of digestion becomes a poison, altogether so adding to the toxic condition that nature finally ends an evil she can not cure. After a vigorous expulsive efforts, for example, the system, temporarily quiescent, gathering fresh strength for a renewal of the conflict to dislodge the enemy, or, possibly, having already accomplished the main work, now rests in the stage preceding convalescence——is supposed to require the aid of a stimulant, and food also must be given at frequent intervals “to prevent the patient from sinking;” but alas, this proves the weight about his neck that carries him to the bottom——“supported” to death. In comparing the stimulation of the vital organism, in sickness, to the spurring up of a tired or lazy animal to greater exertion, there is always this grand difference: the former will every time, and always, exert its entire force, that is, will exert it better, more savingly to life, without, than with, stimulation. “Self-preservation is the first law of nature;” and no other circumstance possible to imagine, better illustrates this law, than the living organism in sickness.