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