BASAL METABOLISM. 73 



as the experiments were made in the daytime, when the men were for 

 the most part awake. Theoretically the 8-hour period experimental 

 plan would have been very satisfactory if it had been possible for the 

 subjects to sleep throughout the period and thus provide an ideal con- 

 dition for measuring the quiescent metabolism. With many people 

 there is a tendency to sleep after eating; our subjects, however, were 

 nearly all young, many of them being college students; sleep after 

 eating was therefore not a common experience; hence a uniformity 

 in sleep could not be accepted as certain. 



These experiments were subdivided into 2-hour periods and in the 

 Boston experiments into periods even shorter. There was therefore 

 opportunity to secure information as to the time relations of the 

 increase in the metabolism and possibly the maximum effect of the food. 



Many of the disadvantages found with the 24-hour plan apply, also, 

 to the 8-hour method. The possible errors in the measurements are 

 the same as with the longer periods, especially with the large chamber 

 at Wesleyan University, but with the shorter periods thej^ assume 

 more importance, since there is less opportunity for compensation and 

 the total amounts are smaller. Furthermore, with the protein-rich 

 diets, the total effect of the ingestion of food is not obtained, as it is 

 unquestionably true that the stimulus frequently continues longer 

 than 8 hours. During the 8-hour period only one or two meals can 

 be given; the daily routine, with period of sitting or lying after food, 

 must therefore be sacrificed. 



Finally, if we use as a basis of comparison the metabolism deter- 

 mined in an 8-hour period without food, as was done in all of the Mid- 

 dletown experiments considered in this section and in some of the 

 Boston experiments, we must still rely upon the determination of the 

 base-line on one day and the observation of the food period on a sub- 

 sequent day. In the 24-hour experimental plan the periods usually 

 succeeded one another without interval, with the subject under careful 

 surveillance the entire time and with like muscular activity throughout 

 the days compared. In comparison experiments with an 8-hour basal 

 unit, a period of some 8 to 14 hours, and sometimes one or more weeks, 

 may intervene between the fasting and food measurements. During 

 this time the subject is not under supervision; the activity and possibly 

 the diet are therefore not known. The influence of a previous diet, 

 muscular activity, and psychical excitement is as yet too uncertain 

 for us to assume with surety that the basal metabolism will be alike 

 during the periods compared, for although there is a general agreement 

 between experiments made in this way, the katabolism does not remain 

 exactly the same from day to day, either with or without food. Even 

 when we average the results of a large number of fasting experiments 

 and deduct this average from the results obtained after food to find the 

 increase in the metabolism due to the ingestion of food, the errors 



