60 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



noted with A. L. L. being absent. We have here, therefore, the singu- 

 lar fact that this diet was sufficient to raise the metabolism after 7 

 days of fast to the initial level of the first 2 days of the fast, while in the 

 experiment with the same subject on February 2 to 5, a diet containing 

 about 300 more calories was not able to produce this effect. An 

 analysis of the character of the diet shows that the percentage of 

 protein was essentially the same in both instances, but that the carbo- 

 hydrate contained double the amount of energy in this experiment, 

 with a corresponding reduction in the proportion from fat. It is not 

 impossible, therefore, that the action of the carbohydrate accounts for 

 the apparent discrepancy between the two sets of results. Since 

 even in this experiment there was no evidence of an increment if the 

 first 2 days of fasting are taken as a base-line, we can consider the stimu- 

 lating effect of the food as simply compensating for the decrease in the 

 metabolism produced by the specific effect of the fasting. It is only 

 when this depressing influence of fasting has been completely overcome 

 that the stimulating action of the food is apparent. In the plan 

 of experimentation thus far used it is clear that the problem is dis- 

 tinctly complicated by the conditions involving the depressant effect 

 of a prolonged fast and by the attempt to superimpose the stimulating 

 effect of the ingested food. 



As a result of the somewhat unsatisfactory experience with fairly 

 long preliminary fasts, the experimental plan was altered so as to 

 include fasts of only 2 days' duration in an attempt to minimize the 

 depressing influence of the fasting and yet to secure a suitable base- 

 line for determining the influence of food. Several experiments were 

 made on this plan. The fasting data have already been published for 

 most of these experiments, 1 but the results are repeated in abstract here. 



The first series of experiments on this later plan was made with 

 H. R. D., December 5 to 8, 1905, there being 2 days of fasting followed 

 by 1 day with a mixed diet. The metabolism on the 2 days of fasting 

 was remarkably constant, with an average heat production of 1,910 

 calories. On the food day the heat production increased practically 

 190 calories after the ingestion of food having a fuel value of 2,086 

 calories. In this instance, therefore, the fasting did not so depress the 

 metabolism as to make it unresponsive to the stimulus of the ingested 

 food. It should be noted that the percentage of energy from protein 

 was somewhat larger than in the experiments thus far considered and 

 the proportion from carbohydrates was likewise large. The details 

 are given in table 11. 



A series of experiments was also made with N. M. P., December 9 

 to 12, 1905, in which a mixed diet was given. (See table 12.) The 

 fasting experiments do not show so close an agreement as was found 



'Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, p. 222. 



