98 PHYSIOLOGY OF THE NEW-BORN INFANT. 



Although one would expect with a large number of normal new-born 

 infants to find a tendency towards constancy in the minimum metabo- 

 lism, this chart shows clearly that there is no such constancy, for while 

 in general there is a rough relationship between the total body-weight 

 and the total minimum metabolism, in that for the most part the 

 infants with the larger body-weight have the larger metabolism, yet 

 wide deviations from the average value are found. 



Recently it has been the custom among some writers on metabolism 

 to consider a plus or minus metabolism of 10 per cent as a possible nor- 

 mal fluctuation. Although the arbitrary selection of this range seems 

 questionable and we are unable to see what particular value the indi- 

 vidual normal figures may have when the variation may admittedly 

 be 10 per cent, we have indicated these limits on the chart by light 

 lines above and below the heavier line showing the average value. 

 Even under these circumstances we find that a large number of the 

 plotted figures lie outside of the supposedly acceptable limits of varia- 

 tion, for 13 points are above the upper light line and at least 17 

 points below the lower light line; in other words, some 30 values lie 

 outside of the 10 per cent limits of variation. Perhaps the most 

 striking illustration of this fact is that of an infant weighing 4.1 kilo- 

 grams and having a total heat-output per 24 hours of 133 calories. 

 While the majority of the results obtained were well within the 10 

 per cent limits, yet, as our observations were made with new-born 

 infants, presumably healthy organisms, which should be perfectly com- 

 parable, it is somewhat surprising that variations are found as large as 

 and, indeed, much larger than 10 per cent. 



MINIMUM HEAT-OUTPUT PER KILOGRAM OF BODY-WEIGHT 



PER 24 HOURS. 



The highest value for the minimum heat-production in this series 

 of observations was secured with infant No. 67, who had a body-weight 

 of 4.74 kg., this being the largest body- weight of any of the infants; 

 the lowest minimum heat-production was found with infant No. 82, 

 whose body-weight was only 2.74 kg., although some of the infants 

 had an even smaller body-weight than this. It is obvious, therefore, 

 that body-weight plays an important role in the amount of the katabo- 

 lism and the heat-production per unit of weight must be considered. 

 The values for the heat-production per kilogram of body-weight given 

 in table 12 vary from 52 calories per kilogram with infant No. 50 to 32 

 calories per kilogram with infants Nos. 84, 101, and 104. It is thus 

 clear that, even per kilogram of body-weight, healthy new-born infants 

 may vary widely in their energy output. 



Here again the general trend may be more easily seen in the form of 

 a chart, and the values are therefore given on this basis in figure 5, 

 which shows very clearly the wide variations in the values. Prac- 

 tically no approximation to regularity is apparent, although a con- 



