190 



PULSE. 



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 value, 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 

 Medicina 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, 1 732. 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 an 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 presumption, 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 Nickt 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- 



* A minute account of the experiments of Robin- 

 son and Falconer, and of the literature of this part 

 of the subject of the Pulse, will be found in the Me- 

 dical Gazette, June 10. 1839. KeilPs observations, 

 from which the averages are calculated, amount to 

 256 in the morning, and 275 in the evening ; the 

 observations of Bryan Robinson were continued for 

 twelve weeks in the first case, and three weeks in the 

 second; while the observations of Falconer were 

 continued almost daily for more than three months. 



f Op. cit. D. 513. 



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. M. and ending at 

 10 P. M., a pulse of 59 for the first named hour, 

 and 64 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 

 4 past 10 P.M. In the one case, therefore, 

 there was an increase towards evening of 5, 

 and in the other of 2 beats. When, 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. M., and 58 at 7 p. M., 

 being a difference of 5*8 beats. 



The credit of propounding a diminished 

 frequency of the pulse towards the afterpart 

 of the day, as the true theory, is due to Dr. 

 Knox*, who made several series of experi- 

 ments, in order to establish it. The general 

 results of these experiments with those of the 

 writer, and some facts gleaned from other 

 sources, are thrown together in a table.f 



As the true state of the case did not seem 

 to be made out even by this balance of autho- 

 rity, it was thought desirable to add to the 

 number of observations. Accordingly several 

 averages of the number of the pulse .the first 



* Ed. Med and Surg. Journal, vol. xi. p. 53. 1815. 



f The second and third experiments of Dr. Knox 

 were made after dinner and supper respectively. 

 For full particulars of his other experiments the 

 reader is referred either to the original essay or to 

 the Medical Gazette, June, 1839. An account of 

 the writer's experiments will be found in the Guy's 

 Hospital Reports, No. viii. Dr. James Saunders' ex- 

 periments were not made with any view to this ques- 

 tion, but as a preliminary to the effect of digitalis 

 on the pulse (Treatise on Pulmonary Consumption). 

 Except when taking large doses of the drug, the 

 pulse retained in this respect its normal character, 

 being, in three experiments (dose 15 drops twice a 

 day), 70 in the moming and 66 in the evening, and 

 in two experiments (dose 25 drops), 76 in the morn- 

 ing and 70 in the evening ; but Avhen the dose was 

 raised to 50 drops twice a day, the pulse became 80 

 in the morning and 90 in the evening, and, on the 

 following day, when the dose was again reduced to 

 25 drops, it remained at the last named numbers. 

 From some experiments on the pulse, which form 

 part of Dr. Prout's Essay on the quantity of car- 

 bonic acid emitted from the lungs during respiration 

 (Annals of Philosophy, vols. ii. and iv. 1813), it 

 would appear that the morning and evening fre- 

 quency was very nearly the same, the eleven ob- 

 servations in the morning, which correspond with a 

 like number in the evening, giving as averages 70'91 

 and 70-27. 



