be taken up gradually, and feats requiring a large outlay of physical
energy should be attempted only after long periods of training.

Since the heart is controlled by the nervous system, it frequently becomes
irregular in its action through conditions that exhaust the nervous
energy. Palpitations of the heart, the missing of beats, and pains in the
heart region frequently arise from this cause. It is through their effect
upon the nervous system that worry, overstudy, undue excitement, and
dissipation cause disturbances of the heart. In all such cases the remedy
lies in the removal of the cause. The nervous system should also be "toned
up" through rest, plenty of sleep, and moderate exercise in the open air.

*Effect of Drugs.*—A number of substances classed as drugs, mainly by
their action on the nervous system, produce undesirable effects upon the
organs of circulation. Unfortunately some of these are extensively used,
alcohol being one of them. If taken in any but small quantities, alcohol
is a disturbing factor in the circulation. It increases the rate of the
heart beat and dilates the capillaries. Its effect upon the capillaries is
shown by the "bloodshot" eye and the "red nose" of the hard drinker.
Another bad effect from the use of much alcohol is the weakening of the
heart through the accumulation of fat around this organ and within the
heart muscle. The use of alcohol also leads in many cases to a hardening
of the walls of the arteries, such as occurs in old age. This effect makes
the use of alcohol especially dangerous for those in advanced years.

Tobacco contains a drug, called nicotine, which has a bad effect upon the
heart in at least two ways: 1. When the use of tobacco is begun in early
life, it interferes with the growth of the heart, leading to its weakness
in the adult. 2. When used in considerable quantity, by young or old, it
causes a nervous condition both distressing and dangerous, known as