TUE PULSE.- This subject demands a more minute examination than it has yet received; for it is extremely/ interesting in a physiolo gical point of view. All the older and several comparatively modern authorities agree in representing the pulse as more frequent in the evenim, than in the morning. Hallert, Rye and ?chwenke t, Gregory §, Zimmerman Hufeland 11, Quetelet**, Foderett, Falco ner$1, Double, and Cullen, and, among mo. dern physiologists, Dr. Bostock §§, describe an increase of frequency towards evening ; and more than one of these authors speak of a similar change occurring at noon and in the afternoon. Cullen especially insisted on this latter circumstance.
It will facilitate our inquiry if we confine our attention for the present to the frequency of the pulse in the morning and in the even ing, or in the earlier and later periods of the day, reserving the alleged increase of frequency at noon and in the afternoon for subsequent consideration.
The earlier authorities who have been cited as favourable to an increase of frequency towards evening were not without support from actual experiments, though those experi ments were made in ignorance or disregard of some essential circumstances which tended to impair their vdlue, such as the effect of pos ture and of food and exercise.
The earliest series of experiments which admits of being employed for the purpose of deciding this question is that contained in the Illedicina Statica Britannica of Keill, published in 1718, and which the writer has been at some pains to analyse. Next in order of time are the tables of Bryan Robinson, published in his Animal Economy, 1732. The last series of facts, in confirmation of the opinion of the older authorities, was published by Falconer, in his Observations respecting the Pulse, pub lished in 1796. It will economise time and space to present the general results of these three series of experiments in a tabular form.* The results of these four series of experi ments would appear to furnish a very strong probability in favour of the theory prevailing among the older authorities of au increased frequency of pulse towards the afterpart of the day ; and if all the experiments had been made in full cognisance of the influence of posture and other exciting causes on the pulse, and with a due regard to those circum stances, they would have been quite conclu sive. Even as it is, they must be admitted to
establish a presurnption, if not in favour of a universal law, at least for a general rule, or for a frequent exception to the opposite theory. Some experiments, however, per formed by Nick t on his own person, of which part were made in the same manner as those of Robinson and Falconer, and part with the precautions just indicated, would lead us to entertain a doubt whether the older authorities may not have been altogether misled by an erroneous or careless mode of performing their experiments. Nick's expe riments, performed in the same manner as those of Keill, Robinson, and Falconer, that is to say, without any unusual precautions, gave, as an average of four series, made on four different days, a pulse of 59 at past 7 A. m. and 64 at midnight ; and as the result of a single series beginning at 5 A. 31. and ending at 10 P. m., a pulse of 59 for the first named hour, and 61 for the last. In each of these experi ments the pulse was more frequent in the even ing by 5 beats. In both these cases the posture was disregarded; but even when, as in Bryan Robinson's experiments, the sitting posture was preserved in all the observations, but other precautions disregarded, similar results were obtained. Thus, in one instance, the pulse was 66 at 6 A. m., and 71 at 8 P. M.; and in an average of three series of observations the pulse, which was 70 at 9 A. m., was 72 at past 10 P. m. In the one case, therefore, there was an increase towards evening of 5, and in the other of 2 beats. VVhen, however, the experiments were conducted still more carefully, the recumbent posture being pre served in all the experiments, all mental and bodily excitement being avoided, no food taken, and the same temperature preserved, an average of six series of' observations gave 63.8 as the pulse at 8 A. nr., and 58 at 7 P. m., being a difference of 5.8 beats.