Stimulus implies no undue exaltation of the activity of any part of the organism. In complete health all parts of the body should work together in unhindered co-operation. Any undue exaltation of a particular function--excessive brain-action, excessive muscular-nutrition, excessive deposit of fat--is a symptom of lowered life, in which the co-ordinating control of the whole system over its several parts is diminished. Stimulus, on the other hand, implies an increase of the co-ordinating and controlling power. Dr. Anstie therefore recommends that the word "overstimulation" be disused, as unphilosophical and self-contradictory. In yet one further particular, current notions need to be rectified before we can proceed. _In no case is the action of a stimulant followed by a depressive reaction._ This seems at first like a paradox. Physiologists have in times past maintained the contrary; and some have even ventured to apply to the phænomena of stimulation the dynamic law that "action and reaction are equal and opposite." But in physiology we shall not be helped much by the theorems of mechanics. In no case is the stimulus followed by any other "recoil" than that which is implied in the mere gradual cessation of its action, just as in the case of food which has been eaten, assimilated, and used up. We quote the following from Dr. Anstie:--"We often hear the effects of strong irritation of the skin, or the mucous surfaces, quoted as an example of the way in which action and reaction follow each other. The immediate effect of such treatment (it is said) is to quicken the circulation and improve the vital condition of the part, but its _ultimate_ result is a complete stagnation of the vital activities in the irritated tissues. The real explanation of the matter is, however, very different. Mild stimulation of the skin (as by friction, warm liniments, &c.) has no tendency to produce subsequent depression; nor has mild stimulation of the mucous membranes (as by the mustard we eat with our roast beef). But the application of an irritant strong enough to produce a morbid depression at all, produces it _from the first_. Thus the cantharidine of a blister has no sooner become absorbed through the epidermis than it _at once_ deprives a certain area of tissue of its vitality to a considerable extent, as is explained by the researches of Mr. Lister.... Here is no stimulation first and depressive recoil afterward, but unmitigated depression from the first."[14] "What has been commonly spoken of as the _recoil_ from the stimulant action of a true narcotic is, in fact, simply the advent of narcosis owing to a large impregnation of the blood with the agent after the occurrence of stimulation, owing to a small one. Thus a man drinking four ounces or six ounces of brandy gradually, has not in reality taken a truly narcotic dose till perhaps half the evening has worn away; previously to that he has not been 'indulging in narcotism'