CHAPTER XIII. 



ANIMAL HEAT. 



As the result of the changes occurring in the tissues, heat 

 is developed. It is not necessary that carbon should be 

 oxidized to C0 2 to produce heat, though this is by far the 

 largest source of supply to the system : any change, hydra- 

 tion, tissue decomposition, muscular contraction, the passage 

 of blood through the vessels, the friction produced by one 

 articulatory surface moving on another, all result in the 

 formation of heat. 



The chief source of continual heat production in the body 

 is the food supplied, and the amount of heat which different 

 articles of food are capable of yielding has been very care- 

 fully ascertained by burning them in an apparatus where 

 the heat given off is absorbed by water, and the increased 

 temperature of the water is the measure of the heat pro- 

 duced. This instrument is termed a calorimeter. The 

 measurement of beat produced in the calorimeter is known 

 as a heat-unit, or calorie, and one heat-unit is equivalent 

 to 2*2 lbs. of water raised 18° Fahr. 



The following is Frankland's table of heat-units for 

 different substances : 



1 gramme (15 - 432 grains) of Albumin yields 42G3 heat-units 



