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. Boecker 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.

This peculiar principle (theine) is also found in the leaves of the Ilex Paraguayensis, or Paraguay tea, used in South America, as a beverage.

“Good black tea contains of theine from 2.00 to 2.13 per cent. 
Coffee-leaves contain of theine from  1.15 to 1.25 per cent. 
Paraguay tea contains of theine from    1.01 to 1.23 per cent. 
The coffee-berry a mean of              1.00         per cent.

“Besides the theine and the essential oils, which latter give the aroma of the plants, there is contained in both coffee and tea a certain amount of difficultly soluble vegetable albumen, and in the