1050 



EXPERIMENT STATION RECORD. 



In Period B tho energy of food, minus excreta, is 9,394 calories, and 



the (•()iitri])ution from bod}' tissue 902 calories (or 807 calories as com- 

 puted from the loss of protein and fat), making' a total re<(uirement of 

 10,290 calories of energy, which was evolved by the body as heat. 



A comparison of the two periods shows that the extra hay given in 

 Period P supplied, after deducting the losses in the excreta, 2,S92 

 calories more of energy for the uses of the body and that this dimin- 

 ished the draft on the body tissues for energ}' by 1,811 calories. In 

 round numbers, then, 63 per cent of the added energy was available 

 to diminish the loss of tissue — that is, for maintenance. 



Our final comparison of the two periods, then, takes the following 

 form, in which, for convenience, the losses are expressed as negative 



gains: 



Gains or losses in the animal body. 



Food: 



Proteids digested grams.. 



Total organic matter digested ...do 



Energy snpplied calories. . 



Body rliangrs: 



Gain of i)r<itein grams. . 



Gain of fat do 



Gain of energy calories. . 



Difference. 



26.4 

 708.6 

 2,892 



42.0 



178.4 

 1,811 



The object of these two periods was to ascertain the actual feeding 

 valuQ, under the conditions of the experiment, of 1,219 grams of 

 timoth}^ ha}' added to the ration of Period A. This we determine, just 

 as in the simplest feeding experiment, by trying it and noting the 

 results, and the value of the latter depends as absolutely in the one 

 case as in the other upon the maintenance of uniform and normal con- 

 ditions of experiment, both external and internal. The dilierence is 

 simply that by means of more refined methods we have been able to 

 make a more detailed, definite, and accurate comparison of results. 



It is evident that the same general method is equally applicable to 

 experiments in which an actual gain is made by the animals, and that 

 the kind and amount of gain made niiiy ])e accurately compared with 

 the supply of matter and energy in the food used to produce it. In 

 fact a large amount of work along this line has been done by Kellner 

 and his associates, a consideration of which would lead us too far 

 afield. In general, the method opens the prospect of being able to 

 predict with a good degree of accuracy the amount and kind of gain, 

 or, otherwise expressed, the amount of energy storage in the body 

 which may be anticipated from the consumption of a given amount of 

 matter or energy in this or the other feeding stufi', while it also enables 

 us to formulate the demands of the vital processes for energy and 

 measure the extra expenditure of the latter required in the digestion 

 and assimilation of the coarser as compared with the more concentrated 

 feeds. 



