16 ANIMAL MECHANISM. 



"We have said tliat forces are produced within the organism. 

 All living beings give out heat and produce work. The- 

 disengagement of these forces is caused by the chemical 

 transformation of food. 



In the living being it is possible to measure approximately 

 the quantities of heat and work produced, and even to estimate 

 the quantity of force contained in f-od ; in order to do this 

 it is sufficient to apply the methods which physicists have 

 employed in the estimation of inorganic forces. 



Thus, a man placed for some time in a bath will yield to 

 the water a certain number of units of heat, which may be 

 easily measured. Applied to the moving of a machine, the 

 force of a man or an animal will produce a number of kilo- 

 grammetrea no less easily to be measured. If the aliment be 

 subjected to the experiments which determine the heating 

 power of different combustibles, it will be found that each of 

 them contains a certain quantity of potential force. Favre and 

 Silbennann have supplied most valuable information, attained 

 by great labour, on this point ; and Fraukland has continued 

 their investigations. We no\v know the calorific power of 

 almost all the alimentary substances, it is, therefore, possible 

 to calculate what free force their complete oxidation will yield 

 either under the form of heat or under the form of work. 



But, as we have seen with respect to combustibles employed 

 for industrial purposes, the oxidation is not always complete. 

 Coal partially consumed, gives solid or gaseous residues, 

 such as coke and oxide of carbon, which, being oxidized in 

 a more complete manner, furnish a certain quantity of heat. 

 In the same way, the residues of digestion still contain non- 

 disengaged force. All these forces ought to be estimated if 

 we want to know how much of their force in tension has been 

 lost by the alimentary matters in passing through the organism, 

 and how much ought consequently to be found again under 

 the form of force in action. The urinary secretion also elimi- 

 nates incompletely transformed products ; the urea and the 

 uric acid contain force in tension, which ought to be taken 

 iuto account in calculations. 



The watery vapour which saturates the air as it comes out 

 of the lungs removes from the organism and cariies away with 



