DISCUSSION OF RESULTS. 151 



muscles and organs of circulation — must have a greater metabolism 

 than the integument, hair, finger nails, etc. ; thus, with a larger propor- 

 tion of active protoplasmic tissue in a body, a greater heat-production 

 would normally be expected. On the other hand, inert adipose tissue, 

 even if it be present in large amounts, would not be expected to con- 

 tribute materially to the heat-production. Hence it would be logical 

 to assume that heavy, fat infants need not necessarily have a greater 

 total heat-production than infants of the same weight having less fat. 

 Unfortunately, in the discussions of infant metabolism presented here- 

 tofore by the various writers, almost no consideration is given to the 

 length 1 of the infant. An infant weighing 8 kilograms, 60 cm. long, 

 has obviously a larger proportion of fatty tissue than an infant of the 

 same weight but 70 cm. long, and on the basis of body-weight alone 

 we should normally expect that the longer, thinner baby, with the 

 smaller amount of fat, would have the larger heat-production. 



As stated in the discussion of table 32 the infants included in our 

 study were, for the most part, under weight. There would thus be 

 a deficiency in fat, and possibly a deficiency in the active protoplasmic 

 tissue, but all of the evidence points to the fact that a large part of 

 the discrepancy in weight must have been due to a deficiency in fat. 

 In considering our infants, it should be borne in mind that the actual 

 body-weight on these or similar charts does not give the slightest 

 indication as to the probable chemical composition of the body, par- 

 ticularly with regard to the proportion of fat or of active protoplasmic 

 tissue. The great lack of uniformity in the total heat-production of 

 24 hours, when considered on the basis of body- weight, may, therefore, 

 be considered as possibly explained by variations in the chemical com- 

 position of the bodies of the different infants, i. e., in the relative 

 proportions of fat and active protoplasmic tissue. Accordingly the chart 

 in figure 53 is chiefly of interest as indicating in this group of infants, 

 as a whole, that there is no definite uniformity between body-weight 

 and total heat-production for 24 hours in infants under uniform con- 

 ditions as to muscular activity and general repose. 



HEAT-PRODUCTION PER KILOGRAM OF BODY-WEIGHT. 



A method commonly used for the comparison of individuals of 

 different body-weights is to compute the metabolism on the basis of 

 per kilogram of body-weight. Thus differences in total metabolism 

 ascribable to body-weight alone are eliminated. Accordingly in the 

 chart in figure 54 we have presented the heat-production per kilogram 



: In this connection it should be noted that owing to the stimulating suggestions of Rubner, 

 great emphasis has been laid upon the computed body-surface of infants and its relation to the 

 total metabolism. Aside from the formula of Miwa and Stoeltzner (Zeitschr. f. Biol., 1898, 36, 

 p. 314) for computing the body-surface of infants, all formulas, including those most extensively 

 used at the present day, disregard completely the length of the infant in computing the body- 

 surface, and the computation, therefore, rests upon a determination of the body-weight — the only 

 measured value introduced into the formula. 



