xMay, 1929] SIMPLIFIED TECHNIQUE FOR MEASURING ENERGY 



29 



An ideal experiment thus involves records of the insensible perspiration 

 (iver a period of 24 days, divided as follows: 



7 days preliminary feeding 

 14 " feeding, with digestion balance and metabolism meas- 

 urement during last two days and 



1 day fasting followed by 



2 daj^s fasting with metabolism measurements and determina- 



tion of urinary nitrogen output 



With suitable equipment and organization for conducting an experiment 

 of this order the work involved (excepting of course the periods of metabo- 

 lism measurements) requires the time of two dependable assistants to 

 weigh and water and to feed the animals, and to collect and to weigh ali- 

 quot samples. With four animals at our laboratory this procedure re- 

 quires the time of one man for a quarter of an hour in the morning merely 

 to check off any left-over feed and to put a fresh feed into the mangers, the 

 rations being weighed out in advance. In the evening it requires the serv- 

 ice of two assistants for about one hour, to feed the animals and to per- 

 form the other requirements mentioned above. The general results of 

 such an experiment are illustrated in Tables III and IV. 



T.\.BLE IV- 



-Average daily dry matter, protein, and heat of combustion in feeds, feces and urine during digestion 



balance 



T^- ,-uv^ r-D *• 570-280 ^,„ .^x- .u-,-. ci:< 33610-12690 „„^ 



Digestibihty of Protein — -— — =51 %• Digestibihty of Energy „„,,„ =62%. 



570 ooolU 



1 Estimated heat of combustion. 



2 Based on period 13, Table 27, Steer A (Pub. 324). 



'Calculated on basis of period 13, Steer A, Table 33. Pub. 324, Cam. Inst, of Wash. 



'Based on Discussion page 159, Pub. 324 (factor 12.63 cals. per gram nitrogen, period 13). 



