DYNAMICS 155 



clearly brought out in the experiments described by Kellner. 

 It was found that when a quantity of linseed cake, equivalent 

 to 100 kt. of available energy, was added to a previously 

 determined maintenance ration, F pounds of fat were stored 

 up in the animal's body. The quantity of decorticated cotton 

 cake equivalent to 100 kt. of available energy produced a like 

 result an increase of F pounds when added to the main- 

 tenance ration. It was shown that this increase is the maxi- 

 mum obtainable ; the corresponding amounts of nutrients in 

 the form of pure digestible protein, fat, and carbohydrates 

 produced no more. 



The same is true of various other cakes and meals, but it 

 is not true of hay and straw. The quantity of hay equivalent 

 to 100 kt. of available energy produced only 0*6 F, or 0-7 F 

 pounds of fat, i.e. from 30 to 40 per cent, less than might have 

 been expected. The quantity of straw equivalent to 100 kt. 

 of available energy produced only 0*2 F, or 0*3 F pounds of 

 fat, i.e. from 70 to 80 per cent, less than might have been 

 expected. 



The energy which has disappeared 30 to 40 per cent, in 

 the case of hay, and 70 to 80 per cent, in the case of straw 

 is accounted for by the work done in digesting these fodders. 

 This conclusion is confirmed by the fact that when the straw 

 was supplied in the finely ground condition so as to reduce 

 the work of mastication and digestion, only about 35 or 40 

 per cent, disappeared ; and when it was reduced to pulp by 

 processes similar to those used in papermaking, only about 

 20 per cent, disappeared, i.e. were expended in the work of 

 digestion. 



The results mentioned above were obtained in experiments 

 with ruminants. Pigs and horses have inferior digestive 

 powers (p. 107), and are unable to utilise so much of the 

 energy of coarse fibrous fodders as the ruminants. In fact, 

 it has been shown that these animals may expend more energy 

 in the work of digesting very coarse fodders than they get out 

 of them. A horse fed entirely upon straw died of exhaustion 

 (practically starvation) after about two months, although it 

 was allowed an unlimited quantity of that fodder. 



