Variations in Metabolism. 249 



since they were obtained by the subject himself and of necessity only during the 

 waking hours. The relationship between the average pulse-rate for the day and 

 the metabolism was so striking it seemed desirable to make further experiments 

 to study the relationship between the pulse-rate and the metabolism. 



In order to avoid the errors incidental to the taking of the pulse-rate by the 

 subject himself we used a pneumograph, which was placed around the chest of 

 the subject and the pulse was counted from the minor vibrations of the pointer. 

 In many experiments this method was very successful, in others the results 

 were not so satisfactory, as frequently, particularly during sleep, the subject 

 would unconsciously move into such a position that the pneumograph would 

 not properly register. In a number of experiments a sufficiently accurate count 

 was made to enable us to present the results together with the corresponding 

 metabolism. The values have been collected in table 105. 



It is seen that the pulse-rate increases during the waking hours of the day as 

 compared with the night. The results show conclusively that the pulse-rate is 

 a general index of the metabolism, and indeed, we can obtain an approximate 

 idea of the total metabolism from the pulse-rate of a subject, although the rate 

 per minute of itself is not necessarily a general index of the katabolism for all 

 individuals. One subject may have a high pulse-rate per minute with a lower 

 general katabolism than another who has a much lower pulse-rate. It was seen 

 early in the experimenting that the numerical value of the pulse-rate had no 

 relation whatever to the absolute values for metabolism, but relatively speaking, 

 on the same individual with a low pulse-rate there would be a lower metabolism 

 than with a higher pulse-rate. The results of the investigation here reported 

 are only tentative, and it is hoped by means of a stethoscope, which is more 

 accurate than a pneumograph, to obtain values which may serve for better 

 comparisons in subsequent experiments. 



It is furthermore clear that while the pulse-rate may give a general index of 

 the increased katabolism and of the internal muscular work, including muscu- 

 lar tonus, it is highly probable that the blood-pressure also plays an important 

 role in the total katabolism and that one should know not only the pulse-rate 

 but also the blood-pressure. It is not inconceivable that there may be some 

 relationship established between the two factors, pulse-rate and blood-pressure, 

 on the one hand, and metabolism on the other. It is with this in mind that 

 special experiments are now in progress in the Nutrition Laboratory. The 

 value of such observations for bedridden patients is obvious. It is not easy to 

 determine the total energy output of a bedridden patient, but with a given 

 body-weight and a given pulse-rate and blood-pressure, it may be possible to 

 form an approximate idea of the total katabolism from these factors. At least 

 it would appear that variations in the two factors may prove of value in judging 

 of variations in the metabolism. 



In considering the results given in table 105 it is necessary to bear in mind 

 that there is no attempt to compare muscular activity in the different experi- 

 ments, and the sole basis for comparison is the pulse-rate. As a matter of fact, 



17* 



