30 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



EXPERIMENTAL CONDITIONS. 



Usually the length of the observation was determined solely by the 

 degree of repose of the subject. When the pulse-rate had fallen to a 

 normal level and the kymograph record showed the child was abso- 

 lutely quiet, the measurements of the metabolism were begun. If a 

 normal pulse-rate and satisfactory kymograph record could not be 

 obtained, the observations were discontinued for that day. The 

 measurements of the metabolism were divided into periods of 20 or 

 30 minutes, the number of periods usually depending upon the con- 

 ditions. Since to obtain ideal conditions for measuring the basal 

 metabolism there must be no food in the stomach, the measurements 

 were made in this way whenever possible. 



With the older children, voluntary muscular control and absence of 

 food in the stomach could usually be secured. With young infants, 

 however, the ideal conditions for studying basal metabolism could not 

 be obtained, particularly as to the absence of food in the stomach. 

 In the normal physiological state, the infant has more or less food in 

 the stomach in process of digestion. The infant's natural protection 

 against the lack of such food is restlessness, major activity, and crying. 

 In consequence, when we attempted to secure the post-absorptive 

 condition, we were almost invariably confronted with the fact that we 

 no longer had a quiet infant, that is, one in muscular repose. Of the 

 two factors affecting basal metabolism food and muscular activity 

 the latter is so much the greater that our only alternative was to 

 allow a minimum amount of food and thus secure muscular repose. 



This presence of food in the stomach during the observation con- 

 taminates our comparable data, but was an experimental condition 

 which, for the most part, it was impossible to eliminate with our 

 youngest subjects. Schlossmann and Murschhauser 1 attempted to 

 study the metabolism of an infant during prolonged hunger by giving 

 water sweetened with saccharine and salted. The influence of the 

 hunger was that commonly observed with adults, namely, a distinct 

 increase in acidosis. Experiments with adults have shown that acidosis 

 stimulates metabolism, the acid unquestionably reacting upon the 

 cells, stimulating them to greater activity. Accordingly, as set forth 

 in an earlier publication, 2 it becomes a difficult matter to determine 

 the exact points at which the post-absorptive condition begins and 

 ends and hunger with stimulating acidosis begins. 



While we have in a number of our experiments been obliged to allow 

 food in the stomach during the observation, on the other hand an 

 examination of our data shows that in most of the observations with 

 the younger children the subjects were asleep. In other words, at 



1 Schlossmann and Murschhauser, Biochem. Zeitschr., 1913, 56, p. 355. 



2 Benedict and Talbot, Carnegie Inst. Wash. Pub. No. 201, 1914, p. 147. 



