We have already seen that stimulants such as acids do not produce force, they merely alter its distribution in time. When an acid causes feelings of well-being and an increased excretion of urea, it merely causes the metabolism of a certain amount of albumen which was there before and independent of it; it merely alters the time relation of the metabolism of this albumen, converting it quickly into available force and urea in one hour, while without the stimulant the same albumen might have been slowly converted into force and urea over three or four hours.

But after the force has been produced and the urea excreted, the body is poorer in albumens than it would have been at the same hour if no stimulant had been taken; and the urea curve falls more quickly, as we have seen in chapter i., fig. 5, than if there had been no stimulation.

Such stimulation, therefore, is followed, so long as no fresh albumen is introduced from without, by an exactly corresponding depression, as the body has to economise in the following hours to make up for the increased loss of force in the hour of stimulation.

It is no doubt sometimes necessary for the preservation of life that an extra quantity of force should be available in a given time, and nature provides for this need by keeping a reserve of albumens in the blood and tissues, and the natural stimulant of a call for extra force and exertion brings this reserve out and uses it up; a corresponding rise of urea showing what has taken place.

But as there has been no fresh introduction of albumen and force, the body is poorer in these constituents than before, and has to economise and rest or obtain fresh supplies from without.

And if this is the effect of the natural stimulant, a call for exertion, it must also be the effect of the unnatural stimulant, alcohol; this can introduce no 7 albumen and force, it merely affects circulation and nutrition, and the metabolism of the albumens already in the body, and this call on the resources of the body must be followed by a corresponding depression or economy in the future.

It follows from this that all artificial and unnatural stimulation is wrong, it merely calls out the reserves of force and makes the body poorer in the following period to a corresponding extent, every up is followed by a down, and nothing is really gained by stimulation.

There is, however, one exception to this rule, and that is, when the body is much in need of fresh supplies, and urea has run down so much that force for digestion is scarcely available; a stimulant may here do good by calling out some of the remaining reserves, thus furnishing the necessary force for digestion, and fresh albumens are thus brought more quickly into circulation, and nutrition moves up again.

But even here artificial stimulation may be replaced by rest and economy of force, and is not really necessary if such rest is possible.

Now we have seen that stimulation is merely a call on the reserves of force already in the body, and the more these reserves have already been called upon the greater will be the stimulus required to produce still more; but if the alcohol was itself a force producer, the effect should be the same each time for the same dose.

A food introduces force from without, a stimulant merely calls out force already in the body; and athletes know that they must not take stimulants till near the end of the race, for once their final reserves have been called out nothing is left, and collapse results; but if they took milk in place of alcohol fresh power would result, and go on resulting with each dose of milk.

Now here is a fundamental distinction between a food and a stimulant, and one which is already well known to athletes; it is a point also which can be easily tested by anyone who will take the trouble to do it.

A stimulant increases available force only so long as there is albumen available for it to act upon.

Force is thus proportional to the quantity of food (if within the limits of digestion); but it is not proportional to the quantity of stimulant, and it bears a constantly smaller and smaller proportion to it as stimulation is repeated.

It is useless to argue that force is got out of sugars and starches quite apart from the temporary rise of urea they indirectly produce (fig. 4). If this were so, then they would sustain life indefinitely and apart from albumens, and these last would not be a sine qua non of life; but we know that the contrary has been proved by physiologists, and it can be proved again and again by anyone who will repeat either the experiments of the athletes, or those of which I give figures. Neither alcohol nor sugar is a food in the sense that albumen is.

Now what do we see in nature? If a man is only slightly tired when his urea is falling but his reserves are still fair, a teaspoonful of brandy may set him going for some distance; but at the end of that time his reserves will be considerably reduced, and three or four teaspoonfuls of brandy will now have less effect than the one.

Now just the same holds for those who are constantly resorting to stimulants, they are constantly to some extent drawing on their reserves, and the amount of stimulant will constantly have to be increased as the reserves get less and less, and this again is exactly what we find in nature.

It has been truly said that the man who relies upon stimulants for strength is lost, for he is relying upon a reserve fund which is not completely replaced, and physiological bankruptcy is bound to come sooner or later.

Now this is exactly what the stimulants, such as tea, coffee, alcohol, tobacco, opium and cocaine, do for those who trust in them; they none of them introduce albumen, which would become available for conversion into force and urea, they merely aid the calling out of the reserves.

We may consider that alcohol and tobacco are mere stimulants, and by improving the circulation like the acids previously spoken of, call out a certain quantity of albumen, force, and urea (see fig. 5); but tea and coffee are worse, much worse, for though at first they act as stimulants in much the same way as the acids and alcohol, later on they come into the blood as the very poison uric acid, which is the cause of much of the depression; for we have seen above that fatigue (Physiology And Pathology Of Fatigue) is partly due to deficiency of albumens, and also partly due to deficient tissue circulation, rendering the stock of albumens useless because they cannot get to the tissues; and this defective tissue circulation is the effect of uric acid, to which the xanthins in tea and coffee are equivalent.