THE ENERGY EQUATION. 405 



of metabolism. On the other hand, alcohol shows about the 

 same value in the respiration calorimeter as it shows in the 

 combustion calorimeter, and its metabolic value would there- 

 fore appear high. However the actual food value of alcohol 

 is practically low because limited by its toxic action. 



FOOD CONSUMPTION IN SEVERE MUSCULAR EXERTION. 



In the last chapter reference was made to earlier discussions 

 on the question of the kind of food which must be metabolized 

 to enable the animal organism to do work. By many authori- 

 ties heat liberation was looked upon as an end in itself, and 

 hence foods were divided into the two classes : those important 

 in the production of heat and those important in the produc- 

 tion of outside work. The fats and carbohydrates are found 

 in the first group and the proteins in the second. One of the 

 earliest experimental investigations on the subject was the 

 classic one of Pick and Wislicenus, already referred to. These 

 two men in 1866 made the ascent of the Faulhorn in the Swiss 

 Alps from a known level and determined the excretion of 

 nitrogen, as urea, during and following the ascent. As the 

 elevation to which they ascended was known, it was possible 

 to make some calculations, approximately accurate, of the 

 work done in the ascent. Two things were shown especially 

 by the tests and calculations: there was not a great increase 

 in the urea excreted, and secondly the protein metabolized, as 

 indicated by the urea measured, was not at all sufficient to 

 account for the work done. Their own conclusions were that 

 the protein consumed would not furnish more than half or 

 three-fourths the energy necessary to lift their bodies through 

 the 1956 meters of ascent, to say nothing of the work done in 

 the horizontal direction on a winding pathway, or of the inter- 

 nal work of the body. This experiment attracted a great deal 

 of attention. Frankland made a new determination of the 

 heat of combustion of protein and showed that the value as- 

 sumed by Pick and Wislicenus was far too high, thus making 

 the discrepancy still greater. 



