Theories and Experiments 285 



loss of heat undergone; let us assume also that all the mechanical 

 work is usefully employed, that is, that none of it is lost in slipping, 

 false steps, etc. 



When the body has been raised 1000 meters, the quantity of work 

 accomplished will be represented by 75 x 1000 or 75,000 kilogram- 

 meters. 



As the mechanical equivalent of heat is 425 kilogram-meters for 

 each unit of heat, to get the quantity of heat absorbed during this 



75,000 



work of ascent of 1000 meters, we shall have =176 units of 



425 



heat. If we assume that the specific heat of the human body is equal 

 to that of water, that is, equal to 1, and if we represent this specific 

 heat by C; if we call the drop in body temperature X, we shall have: 

 quantity of heat lost by the body 75 (C + X) or 176 = 75 x X, whence 



176 



X = , or X = 2.3 



75 



Therefore the drop in body temperature resulting from the heat 

 absorbed by a work of 75,000 kilogram-meters, performed in an ascent 

 of 1000 meters, would be 2.3° centigrade, assuming that no combustion 

 repaired, at least in part, this loss of heat. But it is evident that in 

 reality this combustion exists and that a part of the heat expended 

 is restored while it is being absorbed. But we have seen, by the 

 study which we have made of the respiratory and circulatory disturb- 

 ances, how much this combustion is hampered at a certain altitude, 

 and how incomplete it is. 



Furthermore, it is evident also that all the energy expended is far 

 from being useful because of false steps and the softness of the snow. 

 The quantity of heat used must therefore be enormous, and the drop in 

 temperature must be great and hard to meet by respiratory com- 

 bustion. 



We see then, when these different elements of the problem are 

 well considered, that this drop of four and some tenths degrees centi- 

 grade, in the ascent of Mont Blanc, is not at all extraordinary because 

 this figure gives one and some tenths degrees centigrade for each thou- 

 sand meters of elevation, a quantity which is very near the 2.3° centi- 

 grade given us by the physical theory, when we do not take into 

 account the respiratory combustions. (P. 36.) 



However, when one is digesting, there is almost no drop in tem- 

 perature, probably because of the acceleration of the circulation, either 

 general or capillary, and perhaps also because of an extremely rapid 

 absorption of alimentary material. This explains the practical habit of 

 the guides of giving out food about every two hours. Unfortunately, 

 above 4500 meters, distaste for food is so great that it is almost im- 

 possible to swallow a few mouthfuls. (P. 37.) 



To this chief cause others are added, which M. Lortet stresses. 

 First: 



The rapidity of the circulation is another cause of the drop in 



