ICE, WATER, AND STEAM 113 



In cold-storage plants the machinery is similar to that used 

 in making ice, but it is used to cool rooms instead of to cool 

 vessels of water. It is possible to secure in a room a tempera- 

 ture below the freezing point of water, and to keep this tem- 

 perature constant throughout the year. Of course, any degree 

 of cold above the freezing point can be had, and thus it is 

 possible to store each kind of food in the particular tempera- 

 ture that is best suited to it. Cold storage has made possible 

 a supply of fresh foods at seasons when they could not 

 otherwise be obtained. 



126. Perspiration. The bodies of men and of some animals 

 are cooled by evaporation. In the skin there are multitudes of 

 small pores through which water is given off from the body. 

 Usually there is so little water given off that it evaporates as 

 rapidly as it appears, and we do not notice either the water 

 or the cooling effect of the evaporation. When the weather 

 is unusually warm or when we are making great exertion, the 

 perspiration is poured out so rapidly that the surface of the 

 body becomes moist, and if one stands in a draft, the cooling 

 effect is very evident. The cooling is important also when 

 one is not in a draft, though it is not noticed so much. If the 

 perspiration were to stop suddenly, we should quickly feel a 

 rise in the temperature of the body. Indeed, that is what 

 happens in a fever. 



The temperature of the body does not usually vary more 

 than a fraction of a degree. When we feel hot we are really 

 not much warmer than at other times, as would be proved 

 by a thermometer. The temperature remains constant because 

 the amount of water thrown out for evaporation is regulated 

 by the perspiratory glands. But in case of fever the perspira- 

 tory glands cease to work, the skin becomes dry and hot, and 

 the temperature of the whole body rises. If the tempera- 

 ture becomes very high (say four or five degrees Fahrenheit 

 above normal), it indicates a serious condition, and death 

 may result. 



