backwards on each side of the larynx. The
progress of the pulse-wave must not be confused with the actual current of
the blood itself. For instance, the pulse-wave travels at the rate of
about 30 feet a second, and takes about 1/10 of a second to reach the
wrist, while the blood itself is from 3 to 5 seconds in reaching the same
place.

The pulse-wave may be compared to the wave produced by a stiff breeze on
the surface of a slowly moving stream, or the jerking throb sent along a
rope when shaken. The rate of the pulse is modified by age, fatigue,
posture, exercise, stimulants, disease, and many other circumstances. At
birth the rate is about 140 times a minute, in early infancy, 120 or
upwards, in the healthy adult between 65 and 75, the most common number
being 72. In the same individual, the pulse is quicker when standing than
when lying down, is quickened by excitement, is faster in the morning, and
is slowest at midnight. In old age the pulse is faster than in middle
life; in children it is quicker than in adults.

[Illustration: Fig. 79.--Circulation in the Capillaries, as seen with the
Microscope.]

As the pulse varies much in its rate and character in disease, it is to
the skilled touch of the physician an invaluable help in the diagnosis of
the physical condition of his patient.

Experiment 92. _To find the pulse_. Grasp the wrist of a friend,
pressing with three fingers over the radius. Press three fingers over
the radius in your own wrist, to feel the pulse.

Count by a watch the rate of your pulse per minute, and do the same with
a friend's pulse. Compare its characters with your own pulse.

Observe how the character and frequency of the pulse are altered by
posture, muscular exercise, a prolonged, sustained, deep inspiration,
prolonged expiration, and other conditions.

197. Effect of Alcoholic Liquors upon the Organs of Circulation.
Alcoholic drinks exercise a destructive influence upon the heart, the
circulation, and the blood itself. These vicious liquids can reach the
heart only indirectly, either from the stomach by the portal vein to the
liver, and thence to the heart, or else by way of the lacteals, and so to
the blood through the thoracic duct. But by either course the route is
direct enough, and speedy enough to accomplish a vast amount of ruinous
work.

The influence of alcohol upon the heart and circulation is produced mainly
through the nervous system. The inhibitory ner