MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 239 



about .3 of a gram of Lampblack was taken in a gelatin capsule with the food, in order to mark the 

 separation of the feces of the preliminary experiment from those of the metabolism experiment 

 proper. The subject entered the chamber about 7 o'clock on the evening of the last day of the 

 preliminary digestion period and retired about 11 o'clock. At about 1 o'clock in the morning 

 the heat measurements were begun. 



The night sojourn in the chamber sufficed to get the temperature of the apparatus and its 

 contents of carbonic acid and water into equilibrium, so that accurate measurements might begin 

 at 7 o'clock on the first morning of the experiment proper. In some cases the experiment con- 

 tinued only 1 days; in other cases the experimental period consisted of 6 or 9 successive days 

 -pent within the apparatus, the entire period being divided into 3 experiments of 2 or 3 days 

 each with changes in the diet as hereafter explained. The determinations of carbon dioxide, 

 water vapor, and heat were made in 6-hour periods, so that complete data for an experiment 

 showed the total amounts of these compounds given off from the body during the periods ending 

 at 1 p. m.. 7 p. m., 1 a. m., and 7 a. m. of each day of the experiment. As noted beyond, the 

 urine was also collected and its nitrogen content determined for corresponding periods. 



The daily routine of the subject within the chamber was indicated by a programme made up 

 before the beginning of the experiment. A copy of the programme was furnished to the subject, 

 who followed it with reasonable closeness, and other copies were posted in convenient places out- 

 side the apparatus for the benefit of those who had the experiments in charge. 



Much care was necessarily taken in preparing the food materials selected for the diet and in 

 taking samples for analysis. With the exception of milk and alcohol, the proper quantity of 

 eaeli kind of food, either for each meal or for the whole day, was put up in glass jars before the 

 experiment began: and materials which might spoil during the course of the experiment, such as 

 bread and meat, were thoroughly sterilized. 



Special arrangements were made by which the mixed milk from a definite number of select 

 cows was supplied for each experiment. But even with this precaution, the milk was not entirely 

 uniform in composition from day to day. 



The handling of the alcohol was much simpler. A quantity sufficient for several experi- 

 ments was procured and analyzed, and the proper amounts w T ere drawn each day as needed. 



As stated above, the separations of the feces for each experiment were made by means of 

 lampblack. The total feces for each experiment were analyzed, and the average per day used in 

 the computations of results. It was assumed that when the food and exercise were so nearly 

 uniform the undigested residues and metabolic products would not vary greatly from day to day, 

 ami such irregularities as might occur would hardly affect the average for an experiment. 



The urine was collected in 6-hour periods, and the amount, specific gravity, and nitrogen 

 determined for each period. Aliquot portions of the urine of the 6-hour periods were taken for 

 preparation of a composite sample for the day, and in like manner aliquot portions of the com- 

 posite sample of urine for each day w r ere taken for the preparation of a sample for the whole 

 experiment or series of experiments. The nitrogen and heat of combustion were determined in 

 the urine for each day and in the composite for the whole experiment. The carbon and hydrogen 

 were determined in the composite sample of urine for the whole experiment or series of experi- 

 ments, and were divided among the different days in proportion to the amount of nitrogen." 



THE MEN WHO SERVED AS SUBJECTS OF THE EXPERIMENTS. 



Three different men, E. O.. A. W. S.. and J. F. S., have served as subjects in these experi- 

 ments. Each of these, when not sojourning in the apparatus, was engaged in work connected 

 with the investigations. E. O. was a general assistant in the chemical laboratory, a Swede by 

 birth, who had been a number of years in this country; he was 32-33 years old, and weighed 

 about 155 pounds. Since boyhood he had been accustomed to the moderate use of alcoholic 

 beverages. A. W. S. was a physicist, a native of New England, 25 years old. and weighed 



•For further explanation, see U. S. Dept. Agr., Office Exp. Stations, Bui. 69, pp. 21 and 35. 



