Let Me Feel Your Pulse
( Originally Published 1936 )
"The familiar figure of the doctor, watch in hand," as S. Weir Mitchell's phrase is, itself indicates the value of the hints given to the diagnostician by the pulse. It is almost impossible to dissociate our idea of the doctor from his watch and thermometer. And, indeed, these simple instruments of precision give more information to the well-trained mind than many of the expensive tests made by far more elaborate machines.
The pulse at the wrist—the "radial pulse" as we call it, because it is the pulsation of the radial artery—is a reflection of the contraction or beat of the heart transmitted along the exquisitely elastic walls of the arteries to the radial artery itself. If the heart contraction is a heaving one, it is reflected in a large pulse. If the heart beat is a weak one, it is reflected in a small pulsation. If the heart stops for a moment, or if it beats irregularly, this, too, is reproduced with great minuteness in the radial pulse.
The heart beat, under normal conditions, is remarkably regular and similar in all human beings. In adult life it beats a little oftener than once a second--72 times a minute. It is a little faster in child-hood and a little slower in old people. The hearts of different animals also contract at a given rate for nearly every species. The larger the animal, the more likely is the heart beat to be slow.
Of the 7-10 of a second which is occupied by a heart cycle, 340 are taken up with the contraction and 440 with the period of rest or relaxation. The heart muscle needs this period of rest in order to regain its ability to Contract. Why the heart should beat rhythmically, with such even regularity, is a mystery to physiologists, but it is probably wrapped up in the time that it takes the heart to recover from the fatigue of a beat and regain this contractile power.
This rhythmicity is probably inherent in the heart muscle, because strips of heart muscle will contract when removed from the body, if placed in proper solutions.
But the heart also has nervous connections, and one set of nerves which terminates in the heart muscle will cause a rapid beat if stimulated, and another set will cause the heart to slow its rate if stimulated.
No wonder, then, since these nerves arise from the central nervous system, that when we are excited nervously or deeply affected in any emotional way, the rate of the heart changes. The mere excitement of an examination by a physician will often run the pulse rate up 20 to 30 beats, and the experienced physician, in getting the pulse rate, frequently goes back and tries it again, after the patient has become more used to his presence.
The rapid heart beat is probably caused by the output of adrenalin which occurs in conditions of excitement, and which affects the vagus nerve to the heart. The pulse increases in rapidity, however, under many conditions, with nearly all the fevers and in shock, after an accident or injury, surgical operation, etc.
A slow pulse is usually considered by the life insurance companies to be a sign of long life. This is, of course, provided it is not too slow—that is, below 60. It is one of the old rules of thumb that pulses of 60 and thereabouts run in families, and are linked with a tendency to long life.