his apply
to the young, whose bodies are not yet knit into the vigor that can brave
invasion.

The _nicotine_ of tobacco acts through the nerves that control the heart's
action. Under its baneful influence the motions of the heart are
irregular, now feeble and fluttering, now thumping with apparently much
force: but both these forms of disturbed action indicate an abnormal
condition. Frequently there is severe pain in the heart, often dizziness
with gasping breath, extreme pallor, and fainting.

The condition of the pulse is a guide to this state of the heart. In this
the physician reads plainly the existence of the "tobacco heart," an
affection as clearly known among medical men as croup or measles. There
are few conditions more distressing than the constant and impending
suffering attending a tumultuous and fluttering heart. It is stated that
one in every four of tobacco-users is subject, in some degree, to this
disturbance. Test examinations of a large number of lads who had used
cigarettes showed that only a very small percentage escaped cardiac
trouble. Of older tobacco-users there are very few but have some warning
of the hazard they invoke. Generally they suffer more or less from the
tobacco heart, and if the nervous system or the heart be naturally feeble,
they suffer all the more speedily and intensely.

Additional Experiments.

Experiment 93. Touch a few drops of blood fresh from the finger,
with a strip of dry, smooth, neutral litmus paper, highly glazed to
prevent the red corpuscles from penetrating into the test paper. Allow
the blood to remain a short time; then wash it off with a stream of
distilled water, when a blue spot upon a red or violet ground will be
seen, indicating its _alkaline_ reaction, due chiefly to the sodium
phosphate and sodium carbonate.

Experiment 94. Place on a glass slide a thin layer of defibrinated
blood; try to read printed matter through it. This cannot be done.

Experiment 95. _To make blood transparent or laky_. Place in each
of three test tubes two or three teaspoonfuls of defibrinated blood,
obtained from Experiment 89, labeled _A, B_, and _C. A_ is for
comparison. To _B_ add five volumes of water, and warm slightly, noting
the change of color by reflected and transmitted light. By reflected
light it is much darker,--it looks almost black; but by transmitted
light it is transparent. Test this by looking at printed matter as in
Exp