PULSE (Lat. putsus, a pushing or beating). The phenomenon known as the arterial pulse or arterial pulsation is due to the distention of the arteries consequent upon the intermittent injection of blood into their trunks, and time subsequent contraction which results from the elasticity of their walls. It is perceptible to the touch in all excepting very minute arteries, and in exposed positions, is visible to the eye. "This pulsation," says Dr. Carpenter, " involves an augmentation of the capacity of that portion of the artery iu which it is observed; and it would seem to the touch as if this were chiefly effected by an increase of diameter. It seems fully proved, however, that the increased capacity is chiefly given by the elongation of the artery, which is lifted from its bed at each pulsation, and when previously straight, becomes curved; the impression made upon the finger by such displacement not being distinguishable from that which would result from the dilatation of the tube in diameter. A very obvious example of this upheaval is seen in the prominent temporal artery of an old person."—Principles of Human Physiology, 4th ed., p. 492. The number of pulsations is usually counted at the radial artery at the wrist, the advantages of that position being that the artery is very superficial at that spot, and that it is easily compressed against the bone. In some cases it is preferable to count the number of contractions of the heart itself.
The qualities which are chiefly attended to in the pulse are its frequency, its regu larity, its fullness, its tension, and its force.
'the frequency of the pulse varies greatly with the age. In the fetus in titer° the pulsations vary from 140 to 150 in the minute; in the newly-horn infant, from 130 to 140; in the 2d year, from 100 to 115; from the 7th to the 14th year, from 80 to DO; from the 14th to the 21st year, from 75 to 85; and from the 21st to the 60th year, 70 to 75. After this period the pulse is generally supposed to fall in frequency, but the most opposite assertions have been made on this subject. There are many exceptions to the preceding
statement; young persons being often met with having a pulse below 60, and cases not unfrequcntly occurring in which the pulse habitually reached 100, or did not exceed 40 in the minute, without apparent disease. The numbers which have been given are taken from an equal number of males and females, and the pulsations taken in the sit ting position. The influence of sex is very considerable, especially in adult age, the pulse of the adult female exceeding in frequency that of the male of the same age by from 10 to 14 beats in the minute. The effect of muscular exertion in raising the pulse is well known; and it has been found by Dr. Guy that posture materially influences the number of pulsations. Thus, in healthy males of the mean age of 27 years, time average frequency of the pulse was, when standing, 81, when sitting, 71, and when lying, 6 i, per minute; while in healthy females of the same age the averages were—standing, 91; sitting, 84; and lying, 79. 'During sleep the pulse is usually considerably slower than in the waking state. In disease (acute hydrocephalus, for example), the pulse may reach 150 or even 200 beats; or, on the other hand (as in apoplexy and in certain organic affec tions of the heart), it may be as slow as between 30 and 20.
Irregulari& of the pulse is another condition requiring notice. There are two varie ties of irregular pulse: in one, the motions of the artery are unequal in number and force, a few beats being from time to time more rapid and feeble than the rest; in the other variety, a pulsation is from time to time entirely left out, constituting intermission of the pulse. These varieties often concur in the same person, but they may exist inde pendently of each oiler. Irregularity of the pulse is natural to some persons; in others it is the mere result of debility; but it may be caused by the most serious disorders, as by disease of the brain, or by organic disease of the heart; and hence the practical impor tance of ascertaining the various meanings of this symptom.