The pulse may be easily found at the wrist, the temple, and the inner side of the ankle.  The throb of the two carotid arteries may be plainly felt by pressing the thumb and finger 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 nerves, as we have seen, hold the heart in check, exercise a restraining control over it, very much as the reins control an active horse.  In health this inhibitory influence is protective and sustaining.  But now comes the narcotic invasion of alcoholic drinks, which paralyze the inhibitory nerves, with the others, and at once the uncontrolled heart, like the unchecked steed, plunges on to violent and often destructive results.