BY DR. BURDON-SANDERSON. 341 



of heat produced, add to or deduct from the quantity commu- 

 nicated the quantity it has borrowed or given off from its own 

 body. If the animal loses heat while it is in the chamber, 

 the heat it gives off is only partial^ generated, the remainder 

 being abstracted from its own body. If it gains, the quantity 

 of heat generated is only partially given off; the remainder is 

 added to its own temperature. To make this deduction or 

 addition, as the case may be, two questions must be answered. 



1. How much heat does the calorimeter require in order that 

 its temperature may be raised one degree? 



2. How much does the body of the animal require for the 

 same purpose ? 



In both cases the quantity required is equal to the specific 

 heat multiplied by the weight. The mean specific heat of the 

 calorimeter is obtained by adding together the products of the 

 specific heat and weight of the parts of which it is composed 

 i. e., the iron case and the water. 



Supposing, e. g., the iron to weigh 3800 grammes and the 

 water 8600 grammes, the specific heat of iron being 0.114, the 

 product in question is for the iron casing 419.5, while that for 

 the water is 8600.0. Consequently 9019.5 gramme-units 1 of 

 heat are required to raise the whole one degree of temperature. 

 Applying the same method to the animal body, the specific 

 heat of which is estimated to be 0.83, we have of course 0.83 

 gramme-units as the quantity to be added or deducted for each 

 gramme of weight and degree of variation of temperature. 



The whole process will be readily understood from an ex- 

 ample, the weight of the calorimeter being that given above. 



Temperature of calorimeter at beginning 9.l C., at end 

 9.T C. 



Temperature of animal at beginning 39.2 C., at end 

 38.3 C. 



Weight of animal, 3200 grammes. 



From these results we obtain : 



1. Units of heat communicated to the calorimeter 9019.5 x 



1.6 = 14431. 



2. Units of heat borrowed from the body of the animal 



3200 x 0.83 x 0.9 = 2390. 

 Result 144312390 = 12041. 



That is to say, the animal, during the period of observation 

 gave off 12,041 gramme-units of heat. 



In calorimetrical experiments, the temperature of the water 



1 The absolute amount of heat (in gramme-units) required to raise 

 the calorimeter 1 C. of temperature may be ascertained empirically by 

 introducing into the calorimeter (in place of the animal) a metal vessel 

 containing a known weight of water at a known temperature say 40 

 C. and determining on the one hand the loss of heat sustained by the 

 water, and on the other, the gain by the calorimeter in a given time. 



