BASAL METABOLISM. 97 



the temperature curve of the normal body may be reasonably uniform 

 when no food is taken, it is quite likely that the ingestion of food may 

 produce a somewhat rapid rise in temperature which, if not measured 

 accurately, would still further vitiate the calculation of the values 

 for the heat production. It is thus seen that it will be necessary to 

 confine the major discussion of the influence of the ingestion of food 

 upon metabolism to its effect upon the respiratory exchange and the 

 indirect calorimetry computed therefrom, using the grosser heat meas- 

 urements as subsidiary evidence. 



SHORT-PERIOD EXPERIMENTS. 



An examination of the literature (see pages 10 to 46) shows that many 

 of the researches have been carried out with short periods ranging from 

 2 hours to 10 or 15 minutes; the majority of the experiments were made 

 in 15-minute periods. In our study of the metabolism after food a 

 large proportion of the basal metabolism experiments were likewise 

 made with these short periods. 



CRITIQUE OF THE SHORT-PERIOD METHOD. 



This method is particularly adapted for experiments with a respira- 

 tion apparatus with which the gaseous metabolism may be determined 

 and the heat output computed from the results. Such experiments 

 are carried out with considerably less expense and the use of intricate 

 calorimetric apparatus is avoided. Furthermore, comparable values 

 for the metabolism may be obtained on the same day; thus one may be 

 certain of a specially determined and reliable base-line each day, with 

 accurate determinations of body-temperature, pulse rate, and respira- 

 tion rate. 



With both the 24-hour period and the 8-hour period, various time- 

 consuming observations must be made and much duplicate data 

 secured before a satisfactory average is obtained. With the short- 

 period base-line, values may be quickly obtained. Indeed, the results 

 of one or two periods may be rejected on account of extraneous mus- 

 cular activity of some definite nature, and a true base-line may be found 

 from the average of the other periods with more constant results. To 

 avoid possible activity in the rest periods, it has been the excellent 

 custom in Johansson's laboratory in Stockholm to alternate the 

 periods of complete rest with periods of moderate activity and not 

 to insist upon the tedium of an arbitrarily imposed complete muscular 

 rest for any great length of time. 



After two or three periods without food have been obtained with 

 closely agreeing results, and the constancy of the base-line established 

 for that day, food may be given the subject and a series of observations 

 made for from 1 to 6 hours, or even longer. With 15-minute periods 



