138 



GASEOUS METABOLISM OF INFANTS. 



ratus described, but we have seen that this record does not give a 

 comparative picture of the degree of activity of different infants. 

 Consequently, for comparing the maintenance metabolism only periods 

 in which the external muscular activity is eliminated should be used, 

 since in the last analysis knowledge with regard to internal muscular 

 activity is desired, uncomplicated by the increased metabolism due to 

 external muscular activity. We believe that our evidence justifies 

 us in asserting that we have two admirable indices for securing these 

 ideal conditions of muscular repose for comparison, first, the graphic 

 records obtained with the kymograph, and second, the pulse-rate. For 

 comparing the metabolism of different infants, therefore, only those 

 periods with records of complete muscular repose and with minimum 

 pulse-rate can legitimately be employed. 



RELATIONSHIP BETWEEN PULSE-RATE AND METABOLISM. 



From the general pictures of the kymograph curves and the pulse 

 curves, one may infer that the pulse-rate follows closely the muscular 

 activity. Furthermore, since it has been shown that the relationship 

 between the metabolism and the kymograph curves is comparatively 

 constant, it is reasonable to expect that the pulse-rate will follow the 

 metabolism. That this latter relationship is usually more nearly con- 

 stant than the relationship between the metabolism and the record 

 of the muscular activity is clearly indicated in a number of observations 

 in which the kymograph record showed a complete absence of extrane- 

 ous muscular activity, while the pulse records showed fluctuations. 



An excellent illustration of this may be seen in the pulse and kymo- 

 graph curves which were obtained in the observation of February 1, 

 1913, with the infant L. B. (see figure 49). Thus between 4 p. m. and 



PERIOD - II 

 COi per hr 4.14 gms 



PERIOD - III 



C0 2 per hr 3.84 gms 



Pulse 123 



PERIOD - IV 



C0 2 per hr 3.90 gms 



Pulse 122 



- ■* 





-7 



LB. 

 FEB. 1. 1913 



Fig. 49. Pulse-rate and kymograph curves for L. B., February 1, 1913. 



