638 PHYSIOLOGY 



DOG II 



Food Flesh metabolism Condition of dog 



Grm. 



1500 grm. lean meat . 1522 . . Rest 



1500 . 1625 .. Work 



1500 . 1526 . . Rest 



1500 . 1583 . . Work 



1500 . 1535 .. Rest 



During the work days the animal performed about 1500 kilogramme 

 metres in the day. The differences in the protein metabolism between the 

 rest and the work days are thus practically insignificant, the nitrogenous 

 output being determined, not by the work done, but by the amount of 

 protein administered in the food. In the second experiment there is an 

 average increase of protein metabolism during the work days amounting to 

 $6 grm. of flesh, a quantity which is insufficient to furnish the energy of the 

 work done. The same results were arrived at in a classical experiment 

 performed by Fick and Wislicenus on themselves, in which they measured 

 their total nitrogenous metabolism during an ascent of the Faulhorn from 

 the Lake of Brienz. The vertical distance traversed was 1956 metres. 

 During the seventeen hours before the experiment, the six hours of the ascent, 

 and the seven subsequent hours they ate food practically free from nitrogen. 

 The urine passed during the ascent and during the next seven hours was 

 collected in each case and its nitrogen determined. Fick passed 5-74 grm. 

 of nitrogen, which, if the energy of the protein were totally converted into 

 work, would correspond to 63,378 kilogramme metres. In Wislicenus the 

 amount was 5-55 grm. of nitrogen, equivalent to 61,280 kilogramme metres. 

 Fick, who weighed 66 kilos, in raising himself to a height of 1956 metres, 

 had performed 129,096 kilogramme metres, and Wislicenus, with a weight 

 of 76 kilos, had performed 148,656 kilogramme metres. Even if we assume 

 the possibility of a conversion of the total energy of the protein metabolised 

 during the experiment into mechanical energy, we cannot account for more 

 than half of the total work done. All subsequent experimenters have con- 

 firmed the deductions which were drawn from these two researches, namely, 

 that muscular work, while practically without influence on nitrogenous 

 metabolism, increases enormously the carbonaceous metabolism of the 

 body, so that, except in the rare cases where the diet consists of pure protein 

 and the body is practically free from fat, the additional energy output during 

 work is derived from the oxidation of carbon and hydrogen to carbon dioxide 

 and water. 



The general nature of the changes in the metabolism of the body during 

 work is well illustrated by the results obtained by Atwater on man. The 

 total energy output of a man was reckoned as heat by means of the calori- 

 meter. The heat equivalent of the external muscular work performed by 

 the man was also reckoned as heat. In the Table (p. 639) we give the 

 total output of energy per day during rest and work, the latter being also 

 expressed in calories.* 



* One large calorie, or ' kilo-calorie,' is equivalent to 425 kilogrammetres. 



