PULSE-RATE. 81 



possibilities of sexual differentiation, a subject which will be discussed 

 somewhat later in this report, we have tabulated the values for boys 

 and girls separately, those for boys appearing in table 17 and those for 

 girls in table 18. Unlike the average pulse-rates for new-born infants 

 shown in table 16, the pulse data presented in tables 17 and 18 do not 

 represent the pulse-rates obtained in the periods of minimum heat 

 production. The basis of selection here used was the degree of muscu- 

 lar repose, the pulse-rates tabulated being those obtained in periods 

 of minimum activity, as indicated by the tracings on the kymograph, 

 without reference to the heat production. The pulse-rates of boys 

 and girls as presented in these tables offer an opportunity for studying 

 the basal pulse-rate of the same child at varying ages. This is par- 

 ticularly true of boys up to the age of 38 months and of girls up to 

 4 years. 



One of the longest series for boys is that with No. 119. The irregu- 

 larities in the figures reported for this subject show clearly that there 

 is very little evidence of a definitely established trend until the child 

 is somewhat over a year old, but that during the second year there 

 is a distinct tendency for the pulse-rate to decrease. Another long 

 series is represented by No. 158. Here again considerable irregularity 

 is noted previous to the age of 14 months ; thereafter there is a reason- 

 ably uniform decrease. These irregularities during the first 14 months 

 are to be observed with practically all of the boys. During the second 

 year of life, however, the values indicate a definite tendency toward a 

 generally lowering pulse-rate. 



This finding with boys is likewise noticeable with girls, although the 

 irregularity in the first year is by no means so striking. Indeed, with 

 a number of subjects there is a reasonable degree of decrease in the 

 pulse-rate subsequent to the age of 4 or 5 months. It is characteristic 

 of all these children, however, that after the first year and a half the 

 decrease is reasonably well established. 



AVERAGE PULSE-RATE OF CHILDREN. 



The second important factor to which our data contribute is the 

 average pulse-rate of children of the same age, both as to its absolute 

 value and as to the deviation therefrom which can be expected for 

 children in repose. With boys, one of the most extensive series 

 numerically that we have for any age represented in table 17 is that 

 for the group 7 months old, in which the basal pulse-rate for the 13 

 boys ranged from 107 (No. 126) to 127 (No. 154). The average for 

 this group is found to be 117. It is clear, therefore, that it is only 

 with a great deal of reserve that one may speak of the pulse-rate of a 

 boy of 7 months as being 117. Even wider differences are observed 

 with the 4 boys of 20 months, the lowest being 92 and the highest 127, 

 with an average of 111. 



