io8 Physiology. 



ture of the inside of the body. For this it is better to use a clinical 

 thermometer, if one can be obtained. The average temperature of the 

 tissues within the body is about 98.5 F. 



How the Body is like a Stove. The body may be com- 

 pared to a stove. Into one we put fuel and produce heat. 

 In the other we get heat from food. Both take in oxygen. 

 Both produce carbon dioxid, water, and other waste matter. 



How the Body differs from a Stove. But the body is not 

 like the stove in burning the fuel (food) directly. The 

 food is first made into tissues, or material stored in the 

 tissues. It is as though we were to build a stove entirely 

 of coal, and then start a fire in it. In that case it would 

 produce heat not merely by burning in one place within, 

 but would be burning throughout the whole of its sub- 

 stance. This is the case with the body. 



Oxidation in Tissue the Source of Heat in the Body. 



The muscles make up nearly half of the weight of the 

 body. They are more active than most of the tissues. 

 We would naturally infer, as is the fact, that they are the 

 chief source of the heat produced in our bodies. The 

 tissues of the body are oxidizing all the time. But when 

 in vigorous action they oxidize very much more rapidly. 



Production of Heat in the Liver. Next to the muscles, 

 in importance as a heat producer, is the liver, which is the 

 largest gland in the body, and, as we shall soon see, one of 

 the most active. The blood, as it leaves the liver by the 

 hepatic vein, is hotter than anywhere else in the body. 



How the Body is like a Locomotive. But it wiU be better 

 to compare the body to a locomotive, as we produce not 

 only heat, but motion: I. Both are warm; 2. Both 

 move ; 3. Both use fuel (food or coal) ; 4. Both take in 



