500 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



ment. As the season progressed the weather became colder, but the 

 temperatures inside of the group respiration chamber on these nights 

 give no suggestion of change in temperature environment during the 

 various experiments. Furthermore, no evidence has as yet been 

 obtained to show an influence of small changes in temperature environ- 

 ment upon normally-clothed men. The widest variation in average 

 temperatures throughout the entire season's experiments was but 4° 

 C; the average temperature for January 5-6 was 19.3°. We thus 

 have here a perceptible lowering in the basal metabolism for which 

 we have no satisfactory explanation.^ 



Heretofore it has been assumed that the basal metabolism is con- 

 stant,^ particularly when average values are considered, but this group 

 of 12 men, with only minor changes in personnel, showed on the average 

 an actual decrease in the metabolism per kilogram of body-weight 

 amounting to about 11 per cent and a lowering of the metabolism per 

 square meter of body-surface amounting to 9 per cent, in the period 

 from November 4 to January 6. We have no means of knowing to 

 what extent this fall in metabolism is a normal procedure, nor have 

 we evidence as to whether Squad A would have shown a similar 

 lowering, but we must consider the possibilities of having to deal with 

 a normal seasonal fall in basal metabolism of 11 per cent, on the 

 basis of body-weight, or 9 per cent on the basis of body-surface. In 

 any event the value for January 5-6 must be considered as the basal 

 value for Squad B for subsequent comparison. 



To sum up these findings regarding the basal metabolism of Squads 

 A and B, we may say, first, that in the early part of October the two 

 squads gave identical results for heat production in the group respira- 

 tion chamber both per kilogram of body-weight and per square meter 

 of body-surface. The average basal value for Squad A determined 

 with the respiration apparatus in Springfield (see table 113) was 39.5 

 calories, which was but 3 per cent lower than that found with the 

 group respiration chamber in Boston. We thus have three indices 

 of uniformity in the basal values for these squads. Second, the fact 

 that Squad B gave identical values with Squad A indicates that the 

 number of men in the squad was sufficiently large for a general aver- 

 age result. Third, and most difficult to interpret, is the fact that, after 

 4 weeks of constancy, there was a slight seasonal variation in the 

 metabolism, with a tendency towards a decrease in metabolism from 



^ The experiment on the night of January 5 immediately followed the Christmas vacation, the 

 men coming direct from their homes to the Laboratory. The train travel, and the unusual social 

 activities engaged in during the previous 18 days, with consequent loss of sleep, produced fatigue 

 and probably a deeper sleep during the night experiment. The possible factors of fatigue and 

 depth of sleep thus entered into this experiment as in no other one in this series. Attention must 

 be called to the fact that psychological observations on January 5 show, in general, aberrant 

 values which may logically be ascribed to this factor of fatigue. A further complicating feature is 

 the fact that the pulse-rate on the morning of January 6 was, as a matter of fact, 3 beats higher 

 than the last observation on the morning of December 16. This would lead us to expect an in- 

 crease rather than a decrease in metabolism. 



^Benedict and Carpenter, Carnegie Inst. Wash. Pub. No. 261, 1918. 



