PULSE-RATE. 75 



not quite so good as the children in private schools, but better than 

 many of the earlier standards, and consequently may legitimately be 

 regarded as of a degree of normality to satisfy present-day criteria. 



PULSE-RATE. 



One of the most striking indices of apparent changes in metabolic 

 activity, induced either by muscular activity or by febrile conditions, 

 is the pulse-rate. In our earlier treatment of the physiology of normal 

 infants, 1 we laid special emphasis upon the importance of knowing the 

 fluctuations in the activity as exhibited by the kymograph record of 

 the movements of the crib and particularly upon the relationships 

 between this curve for activity and both the pulse-rate and the metab- 

 olism. 



Before the study of new-born infants, our observations on children 

 were so scattered and represented so few normal subjects that we were 

 unable to record normal pulse-rates for children of various ages. 

 With the new-born infants, however, this was perfectly feasible, and 

 in the report of that study, 2 data were recorded giving the average 

 pulse-rate for the first 8 days after birth as 112 on the first day, and 

 for the 7 subsequent days 114, 116, 116, 116, 122, 119, and 126, re- 

 spectively. These average values were obtained from a considerable 

 number of counts for different children. Those for the first day after 

 birth represented 50 new-born infants, but on the later days the num- 

 ber of subjects was less, particularly on the seventh and eighth days. 



In our report of the observations on the few normal subjects, made 

 in the first study of the gaseous metabolism of infants, 1 we were 

 primarily interested in such alterations in the pulse-rate of an indi- 

 vidual infant as were due to changes in activity and not in the altera- 

 tions due to changes in age. Accordingly, in this earlier study the 

 period of observation did not exceed 30 to 45 days, except with a 

 single infant. In the accumulation of our new data, however, special 

 stress was laid upon the trend of the pulse-rate as the age increased. 

 This could be studied advantageously in those series of observations 

 in which the metabolism of the same child was studied over periods 

 of 4 months or more, and in a few cases 3^ years. Finally, with the 

 older children, the unusually advantageous conditions under which 

 the data were obtained make it seem desirable for us to record the 

 pulse-rates and deduce therefrom average values which might be 

 expected from children under quiet conditions. 



Even the earliest observers noted that the pulse-rate of infants was 

 very difficult to obtain and varied under different circumstances. 

 The great difficulties in securing accurate records can perhaps be no 



1 Benedict and Talbot, Carnegie Inst. Wash. Pub. No. 201, 1914. 



2 Benedict and Talbot, Carnegie Inst. Wash. Pub. No. 233, 1915, table 19, p. 115. 



