Sex and minumum pulse-rate

The intimate relation between pulse-rate and metabolism, shown with the same individual in the large majority of observations in this laboratory, makes a careful examination of pulse-rate with respect to sex of special importance. The analysis of data for the basal metabolism of men and women has shown that women as a class have a lower metabolism than men, not only per individual, but per unit of weight. On the other hand, the pulse-rate of women as a class was shown to be higher than that of men, as measurements for 90 women and 121 men in our series gave an average of 68.67 for women and 61.26 for men. These differences are substantiated by the fact that with men three different groups of 28, 116, and 50 men showed average pulse-rates of 62.5, 61.3, and 61.3, respectively. Two groups of women, one of 68 and the other of 22, showed pulse-rates of 69.1 and 67.3, respectively. In other words, it seems thoroughly established that the women as a class have a pulse-rate somewhat higher than men, in spite of the fact that their metabolism is distinctly lower. This supplies very clear evidence that while pulse-rate and heat production may be closely correlated in the same individual, in groups of individuals the pulse-rate may vary enormously and "average" pulse-rate may have little, if any, connection with "average" heat production.

Since the pulse-rates of men and women show a difference, it becomes extremely important, in studying our groups of children, to note at what point, if any, there is a definite change in the pulse-rate, and further comparisons of values for males and females will be of special interest in this connection. Such comparison may be made from the pulse-rate data for boys and girls in table 20, which gives an opportunity of noting the differentiation, if any, due to sex. To this end, wherever values for both boys and girls are recorded at the same age, the higher of the two values has been italicized. Thus, for children I day old, 29 boys gave an average minimum pulse-rate of 113, while 21 girls had a pulse-rate of 110. On the next day the conditions for very nearly the same number of boys as girls were reversed, the girls showing a pulse-rate 4 beats higher than the boys.

Pursuing this method of analysis for the entire group of data in table 20, and passing over those ages for which records are available for only one of the two sexes, we find that at 11 age-periods the boys have a higher pulse-rate than the girls of the same age, while at 15 age-periods the girls have a higher pulse-rate than boys of like age. On this basis, therefore, it would appear that the pulse-rate of the girls was, on the whole, somewhat higher than that of boys. The italicized figures in the table show no great regularity in the appearance of these high values with either sex. The most consistent record is that from 1½ months to 10 months, the only ages at which the girls are not higher being that of 4 months, and again of 5 months, when the average pulse-rate for both sexes is the same. After 10 months the italicized figures indicate but little regularity as to sex.

On the whole, the picture can not be said to speak pronouncedly for a higher pulse-rate with girls than with boys. In making this general conclusion, however, it is important to note that the data under consideration are at best somewhat meager, although they may be relied upon as far as they go. But many observations of the minimum resting pulse-rate of boys and girls are necessary before final conclusions can be drawn, for obviously the pulse-rate at other ages should be studied and supplementary data should be obtained for the higher ages included in our observations.