NUTRITION. 201 



of the cells composing the body, just as the condition of 

 any community depends on the average condition of the 

 individuals of that community. 



Fat as a Tissue. As a tissue fat serves as a stored-up 

 food.' The camel's hump is a well-known instance. In 

 some of the savage races fat is stored in a very similar 

 hump. But in most persons it is distributed more evenly 

 over the body, though there is a tendency to deposit rather 

 more over the abdomen. A fat person can endure starva- 

 tion longer, other things being equal, than a thin person. 

 A layer of fat under the skin serves also as a heat saver. 



Hibernation. Hibernating animals are fat when they enter upon 

 their winter sleep, but are lean when they come out in the spring. 

 Remaining inactive they have produced very little energy, their only 

 motions being a slow and feeble breathing and a correspondingly 

 reduced heart beat. They have consumed the fat, using it mainly in 

 maintaining the necessary heat. In short, they have burned their fat 

 to keep them warm. 



The Hibernation of a Bear. In 'one of Captain Mayne Reid's 

 stories (The Plant Hunters} we are told how the hunters followed a 

 bear into a cave. At the innermost end of this very long cave they 

 finally killed the bear. Just at this time they find that their candles 

 are all burned out, and they are left in complete darkness, lost in the 

 bowels of the earth. Failing to grope their way out, they are at last 

 driven to this expedient : With what combustibles they can gather 

 together, including their gunstocks and some of the fat of the bear, 

 they melt some of the fat, they use the gun barrels for molds, take 

 strips of their clothing for wicks, and make two long candles. With 

 these they finally light their way out to the upper world. 



Respiration and Oxidation of Candle. Now we have seen that 

 when we burn a tallow candle one of the chief products of the combus- 

 tion is carbon dioxid. Another product of the burning is common 

 water. If, then, these hunters had left this bear to his winter's nap, he 

 would have consumed this fat in the slow process of breathing, and 

 it would have given off the same products, as we have proved that two 

 of the waste matters of the expired breath are carbon dioxid and water. 



