208 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



hours was found by computation of results in minimum periods to be 

 285 calories. The child was 22 hours and 31 minutes inside the respira- 

 tion chamber. The total heat-output, calculated on the basis of 24 

 hours, was 372 calories, or an increase of 87 calories (approximately 

 30 per cent) over basal. The second child, E. S., weighed at the time 

 of the observation 5.76 kg. and was 6 months and 1 week old. She 

 was for 23 hours and 10 minutes inside the respiration chamber, 

 giving a total heat-output per 24 hours of 404 calories. Computation 

 of the basal metabolism by the selection of quiet periods gave 338 

 calories, the increase over basal being 66 calories or approximately 

 20 per cent. 



From these two experiments, therefore, it would appear that al- 

 though it is possible for young children to have percentage increases 

 over the basal for relatively short periods of 60 or 70 per cent, or even 

 more, the total 24-hour heat production on the average may be taken 

 as not far from 25 per cent above the basal. These two isolated points 

 at the ages of 2 months and 3 weeks and of 6 months and 1 week can 

 give only a general hint as to the increase in the 24-hour demand over 

 basal. When children are able to leave the crib or cot and actively 

 exercise by creeping, crawling, and walking around, especially older 

 children when running and playing, the increase above basal becomes 

 very great, and our own observations can obviously contribute in no 

 wise to an estimate of the 24-hour demand on this basis. 



The proper estimation of the food needs of growing children can 

 probably never be completely and satisfactorily made from gaseous 

 metabolism experiments. With children, with whom the problem of 

 growth plays so active a r61e, one must supply energy not only for 

 maintenance and for juvenile physical activity, but likewise energy 

 for growth. Even if respiration-chamber experiments were made in 

 which an accurate measurement was made of the entire heat-output 

 for 24 hours of a number of individual children engaging in the usual 

 24-hour day activity, there still would be the growth factor to be 

 allowed for. In any complex of this nature, one is not justified in 

 saying that, since one of the three factors is difficult of estimation, 

 the others can not be satisfactorily determined. If possible, it is 

 important to determine the basal needs and also the need for extra 

 physical activity. 



So far as the basal value is concerned, our experiments, we believe, 

 are reasonably conclusive. So far as the extra needs are concerned, 

 our data supply little if anything of value. The maximum activities 

 noted with children lying in the respiration chamber can, with children 

 over 1^ or 2 years of age, have little meaning. Children below this 

 age are, for the most part, lying either in the bed or crib, and conse- 

 quently these periods of maximum activity can well correspond to 

 those occurring in the life of an ordinary young infant. 



