118 GASEOUS METABOLISM OF INFANTS. 



RECORDS OBTAINED DURING OBSERVATIONS WITH THE RESPIRATION 



APPARATUS. 



The observations just discussed were only preliminary in character 

 and were necessarily liable to more or less error. We have, however, 

 a large number of pulse records which were subsequently made while 

 the infant was under constant conditions in the respiration chamber. 

 These records were likewise obtained by the use of the stethoscope 

 according to the method previously described. 1 



It was frequently noted by the observer that the pulse-rate varied 

 considerably during the minute of counting, particularly with very 

 young infants. Thus, while the pulse-rate might be 20 beats in the 

 first 10 seconds of the count, during the next 10 seconds it might fall 

 to 18 beats, with similar variations throughout the whole minute. 

 The pulse-rate was usually counted for one complete minute, but if 

 the infant was crying it was counted for a half minute. At times when 

 it was impossible to hear the pulse beat, the regular rrrythni was counted 

 by the observer and the count resumed by picking up the beats again 

 when they became audible. Except during periods of crying, the pulse 

 beats could be counted with a high degree of accuracy, but with the 

 rapid pulse of severe crying slight errors unquestionably crept into the 

 count. The arrhythmical pulse-rate of normal infants has recently been 

 very extensively studied by Hecht. 2 



As already stated, we feel that the possibility for error in this method 

 of taking the pulse records is too great and that some automatic form 

 of recording the pulse-rate should be substituted. Every effort was 

 made, however, to obtain pulse records as nearly exact as possible with 

 this method, so that the pulse curves secured during the observations 

 with the respiration chamber may very properly be carefully studied and 

 relationships established with other records obtained at the same time. 



RELATIONSHIP BETWEEN PULSE-RATE AND MUSCULAR ACTIVITY. 



The simultaneous measurements of the pulse-rate by means of the 

 stethoscope and of the muscular activity by the kymograph enable us 

 to make sharp comparisons between these two factors. Such a com- 

 parison is made in figures 20 and 21, in which the kymograph curves 

 obtained with two subjects are compared with the curves for the records 

 of the pulse-rate during the same period of time. 



The pulse and activity curves obtained for E. R. in the observation 

 on April 12, 1913, are given in figure 20. The kymograph record shows 

 that after a period of activity from 3 h 3 m p. m. to about 3 h 16 m p. m. 

 there was a short period of comparative quiet, i. e., from 3 h 16 m p. m. 



!See p. 61. 



2 Hecht, Der Mechanismus der Herzaktion im Kindesalter, seine Physiologie und Pathologie, 

 Ergebnisse d. inn. Med. u. Kinderheilkunde, 1913, 11, p. 324. 



