WORK OF DIGESTING AND ABSORBING FAT 305 



The conclusion from these experiments is that the worth fat 

 is to that of carbohydrate as 95' 5 : 100, while if Chauveau's 

 view were true it would be as 64 : 100. The difference found by 

 Atwater is very small, and may be an individual peculiarity. 

 Rubner also concluded that fat and carbohydrate replaced each 

 other when given in isodynamic amounts. 



In the fasting animal the R. Q. may sink below that of an 

 animal fed on fat. This must be due to the conversion of some 

 proteid or fat into sugar. The same thing may happen in cases 

 of diabetes, and in hybernating animals during their winter sleep 

 (Pembrey). 



To what an extent the depot fat can be used as a source of 

 muscular energy is shown by the following observation of Atwater. 



The subject pedalled the friction bicycle 16 hours out of the 24. 



The whole energy^ expended = 9981 Cal. 



The energy of the food taken = 5138 Cal. 



The energy taken out of the body substance = 4843 Cal. 



The energy derived from tissue proteid only = 478 Cal. 



As the man was in perfect training his muscles were not 

 overdone, and thus the proteid metabolism was scarcely increased. 

 This experiment strikingly shows how surplus body fat can be 

 taken of? by hard muscular work. 



THE WORK OP DIGESTING AND ABSORBING FAT 



The taking of food increases the metabolism of the fasting 

 animal owing to the activity of the digestive organs mastication, 

 peristalsis, glandular secretion, &c. ; the processes of solution, 

 hydration, fermentation, and cleavage; the warming of ingesta; 

 the cleavage and synthetic processes of absorption. The injection 

 of sugar or egg-white into the circulation does not provoke any 

 such increased expenditure of energy (Zuntz, v. Mehring). 



The average metabolism of a fasting man resting in bed was 

 2022 Cal. When over-fed his metabolism became 2517 Cal. 

 (Johansson, Tigers tedt, &c.). 



Fat fed to fasting dogs in 2-3 hrs. increases the 2 use 12 per 

 cent. The maximum is reached in 5-9 hrs., and the effect 

 is over in 12 hrs. A large ration of fat may increase the 

 expenditure of energy 19 per cent. The R. Q. sinks almost to 



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