CHAPTER XV 



CONTRIVANCES FOR REGULATING THE HEAT OF 

 THE HUMAN MACHINE 



On a cold winter's day you have seen a man, with his 

 body somewhat bent, his head drawn down on his 

 shoulders, rub his hands, stamp his feet, and beat his 

 arms. He tells you he is shivering with cold, but when 

 you measure the temperature of his body by placing 

 a thermometer in his mouth you find it is almost the 

 same as your own — at little over 9 8° Fahrenheit (37° 

 Centigrade). Then you meet the same man on a very 

 hot summer's day ; the iron railings which in winter were 

 so cold that they stung when touched are now too hot to 

 hold comfortably ; the man is carrying a heavy burden 

 and sweat drops from his forehead. You again measure 

 his temperature and find it is almost the same as on the 

 coldest day of winter. The iron railings, the sunbaked 

 pavement, the air, and all the man's surroundings have 

 been raised to ioo° in temperature, but the man's body is 

 neither warmer nor colder than before. Engineers have 

 not succeeded in making a moving machine which can 

 maintain the same temperature in all climates and in all 

 weathers. We have seen something of the contrivances 

 which they apply to keep engines cool — the circulation 

 and evaporation of water, currents of cooling air, even 

 the application of clothing, but all of them are mere 

 makeshifts. We are now to inquire into the contrivances 

 which Nature has applied to regulate the temperature of 

 our bodies. 



Our inquiry follows naturally on the two preceding 



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