THE PULSE (Gr. onrypor, creputss, Lat. Pulsus, Fr. Pouls, Ger. Puls, Dut. Pols, Ital. Paso, Span. Pulso).— The nature and cause of the pulse have already been examined in an earlier part of this work.* It is proposed to consider it, in this place, as a separate and independent subject, and to bring together the leading facts which have been ascertained, in reference especially to that property which is most readily submitted to examination, namely, its frequency.
Our knowledge of this subject is little more than a century old ; for though Quetelet f at tributes to Kepler, who was born towards the end of the 16th century, the idea of ascer taining the number of pulsations in a given time, Floyer, who wrote at the beginning of the 18th century, was the first who collected any considerable number of' observations. Bryan Robinson $, Falconer §, K.nox II, Graves IT, Nick **, and Quetelet ft followed in the same field of inquiry, and still more recently the writer of this article. The facts which these authors placed on record have not yet been brought together in any standard treatise on physiology ; so that a clear and connected exposition of the frequency of the pulse, as it is affected by age, sex, posture, exercise, food, and other natural causes, and of the relation which it bears to the respiration,is still a desideratum.
It is true that there is no want of rough esti mates, or of calculations founded on theoretical data ; but there is in this, as in most kindred subjects, a great lack of careful observations, and correct average results. This deficiency it is the object of this article to supply, by presenting in succession the number of the pulse, as influenced by the principal causes already specified.
AGE. —In treating this part of the subject no distinction is made between the sexes, nor is any notice taken of the influence of pos ture, and time of day. The average results are based on the observations made by dif ferent authors on healthy persons of both sexes it a state of rest, and on those of the writer of this article, which, with the excep tion of sery young children, were taken in the sitting posture in the middle of the day, and in a state of rest and abstinence. As
these latter facts form the majority of those from which the averages are calculated, it will be correct to state that the tables pre sent a near approximation to the frequency of the pulse in persons of different ages in a state of rest and abstinence, in the sitting posture, and at or about the middle of the day.
The pulse has its maximum frequency in early infancy, and its minimum in robust old age. Frotn infancy to adult age it continues to fall, and probably attains its lowest point at or about the age of 50, to rise again, if feeble as well as robust persons are included in our observations, in the aged.
Infancy. —The frequency of the pulse is very variable at this period of life. According to Quetelet *, the numbers are as follow.
Max. 165 ; min. 104, ; mean 135 ; range 61.
Other authorities estimate it at 130 to 140, or at the last of these numbers ; but it will assist the memory to fix the average at 140.
During the first few weeks or months of life, the frequency of the pulse in healthy children is rapidly diminished, as appears from the following Table, based on the observations of Billard, in which table the averages must be understood to be approximations.
Hence, then, between the first and tenth day there is a range of 100 beats ; between the fir'st and second months, of SO beats ; and between the second and third months, of 30 beats, with an average fall in the first three months of about 20 beats. The numbers of observations on which these averag,es are founded are, between 1 and 10 days, 56 ob servations ; between 1 and 2 months, 36 ob servations ; and between 2 and 3 months, 20 observations.* It would answer no good purpose to enter more minutely into the fre quency of the pulse at these early periods of life ; it will suffice to present it year by year during the first twenty-five years of life, as is done in the following table, based upon be tween 600 and 700 observations made chiefly by the writer of this article, each average being deduced either from 20 or 25 facts.