As final deductions from these experiments, there result, first, "that, when the diet is sufficient, the body is more likely to gain weight when tea is taken than when not"; second, "that, when the diet is insufficient, tea limits very much the loss of weight thereby entailed."
A set of experiments made by Dr. Lehmann are parallel with these. They exhibit the effects of coffee on the excretion of phosphorus, chloride of sodium, (common salt,) and nitrogen. If less full than Dr. Böcker's, they appear to be equally accurate, and more complete in showing the separate actions of the several constituents of coffee. It would be tedious to the general reader to follow them in detail, and we shall avail ourselves of the brief resumé of Dr. Chambers.
"First,—Coffee produces on the organism two chief effects, which it is very difficult to connect together,—namely, the raising the activity of the vascular and nervous systems, and protracting remarkably the decomposition of the tissues. Second,—that it is the reciprocal modifications of the specific actions of the empyreumatic oil and cafeine contained in the bean which call forth the stimulant effects of coffee, and therefore those peculiarities of it which possess importance in our eyes,—such as the rousing into new life the soul prostrated by exertion, and especially the giving it greater elasticity, and attuning it to meditation, and producing a general feeling of comfort. Third,—that the protraction of metamorphic decomposition which this beverage produces in the body is chiefly caused by the empyreumatic oil, and that the cafeine only causes it when it is taken in larger quantity than usual. Fourth,—that cafeine (in excess) produces increased action of the heart, rigors, headache, a peculiar inebriation, delirium, and so on. Fifth,—that the empyreumatic oil (in excess) causes perspirations, augmented activity of the understanding, which may end in irregular trains of thought, restlessness, and incapacity for sleep."
It follows that both the active elements of the coffee-berry are necessary to insure its grateful effects,—that the volatile and odorous principle alone protracts decomposition,—and that careful preparation in roasting and decocting are essential to secure the full benefits of it as a beverage.
It would be difficult to overestimate the practical importance of these results. They raise coffee and tea from the rank of stimulants to that of food,—from idle luxuries to real agents of support and lengthening of life. Henceforth the economist can hear of their increasing consumption without a regret. The poor may indulge in them, not as extravagant enjoyments, but practical goods. The cup of tea, which is the sole luxury of their scanty meal, lessens the need for more solid food; it satisfies the stomach, while it gladdens the heart. It saves them, too, the waste of those nitrogenized articles of food which require so much labor and forethought to procure. The flesh meats and the cereals, which contain the largest amounts of this requisite of organic life, are always the dearest articles of consumption. Certainly it is not as positive nutriment that we recommend the use of coffee and tea; for although they contain a relatively large amount of nitrogen, that supply can be better taken in solid food. Their benefit is two-fold. While they save more than enough of the waste of tissue to justify their use as economical beverages, they supply a need of the nervous system of no small importance. They cheer, refresh, and console. They thus fill a place in the wants of humanity which common articles of food cannot, inasmuch as they satisfy the cravings of the spirit as well as of the flesh.
We have before attempted to show that the human race is liable to a peculiar and constant waste from the development of the nervous system, and that the body has to answer for the labor of the mind. At first thought, we shall find it difficult to appreciate the endless vigilance and activity of the brain. Like the other organisms which possess a proper nervous system, man carries on the common organic processes of life with a regularity and unfailing accuracy which seem to verge on the mechanical forces, or to be, at least, automatic. All habitual voluntary acts by repetition become almost automatic, or require no perceptibly distinct impulse of the will. When we emerge from this necessary field of labor, we come to those functions peculiar to the proper brain. Here all is continual action. Thought, imagination, will, the conflicting passions, language, and even articulation, claim their first impulse from the nervous centre. The idlest reverie, as well as the most profound study, taxes the brain. That distinguishing attribute of man can almost never rest. In sleep, to be sure, we find a seeming exception. Then only its inferior portion remains necessarily at work to supervise the breathing function. Yet we know that we have often dreamed,—while we do not know how often we fail to recall our dreams. The duality of the cerebrum may also furnish a means of rest in all trivial mental acts. Still, the great demands of the mind upon the nervous tissues remain. And it is these losses which may be peculiarly supplied by the nervous stimulants. Such are coffee and tea. Common nutrition by common food, and particularly the adipose and phosphatic varieties, nourishes nerve tissue, no doubt, as gluten and fibrine do muscle. But the stimulants satisfy temporarily their pressing needs, and enable them to continue their labors without exhaustion. Reacting again upon the rest of the body, they invigorate the processes of ordinary nutrition; for whatever rests or stimulates the nerve proportionately refreshes and vitalizes the tissues which it supplies.
It would be curious and well worth while to follow out the peculiar connection between the use of coffee and the excretion of phosphorus, which has been before hinted at. Other experiments of Dr. Böcker prove sugar to be a great saver of the phosphates, and hence of bone,—which affords, at least, a very plausible reason for the instinctive fondness of children for sweets, during the building portion of their lives.
In exhausting labors, long-continued exposure, and to insure wakefulness, the uses of coffee and tea have long been practically recognized by all classes. The sailor, the trapper, and the explorer value them even above alcohol; and in high latitudes we are assured of their importance in bracing the system to resist the rigors of the Arctic winter.
There is of course, as in all human history, another side of this picture. Abuse follows closely after use. The effects of the excessive employment of nervous stimulants in shaking the nerves themselves, and in impairing digestion, are too familiar to need description. Yet even here abuse is not followed by those terrible penalties which await the drunkard or the opium-eater. Idiosyncrasy, too, may forbid their use; and this is not very rare. As strengtheners and comforters of the average human system, however, they have no superiors, and none others are so largely used.
It is a little singular that the active principles of coffee and tea are probably identical,—no more so, however, than the marvellous similarity of starch, gum, and sugar, or other chemical wonders. They have been called cafeine and theine, respectively. They are azotized, and contain quite a marked amount of nitrogen. Chemically, they consist of carbon 19, hydrogen 10, nitrogen 4, oxygen 4. Some allowance is therefore to be made for them as plastic food.