172 PHYSIOLOGY AND HEALTH. 



every country, from the equator almost to the poles. Under 

 the equator, the temperature of the atmosphere is elevated to 

 100, bodies exposed to the sun are heated to 130, and the 

 inhabitants are there subjected to a perpetual heat. In the 

 northern regions, Captain Parry found the thermometer as 

 low as 55 below zero; and Captain Back found it 15 lower 

 than this, or 70 below zero. These were 87 and 102 below 

 freezing point. And yet, in these extremes of external tem- 

 perature, the internal heat of the human body varies very 

 little. There are greater differences than even this. In 

 France, some bakers entered their ovens heated up to 278, 

 or 66 warmer than boiling water, without increasing their 

 own heat. And some philosophers of London tried the ex- 

 periment, to ascertain how great heat could be borne without 

 injuring or increasing the temperature of the living body. 



402. Sir Charles Blagden entered a room, prepared for 

 the purpose, in which the thermometer stood at 260 ; and 

 there he staid for eight minutes. Eggs were put into the 

 same room, and were soon roasted quite hard. " Beefsteak 

 was not only dressed, -but almost dry." And yet here, in 

 this great heat, in which water boiled and meat was cooked, 

 the thermometer, when placed under the tongue, was raised 

 only to 100, two degrees above the usual standard. There 

 have been many other experiments and observations of this 

 kind, which show the same principle that the heat of the 

 living body does not change, or changes very slightly, with 

 the temperature of the air or water which surrounds it. A 

 dyer will hold his hands in water at the temperature of 130, 

 and the ice-cutter has his hands in contact with ice at 32 ; 

 and, in both instances, the temperature of the body is about 

 the same, neither raised in one case, nor depressed in the 

 other, materially. 



403. There is a natural and almost universal tendency to 

 equilibrium of heat. When a warm and a cold dead body are 

 brought in contact, their heat is shared in common between 

 them. One loses, and the other gains, heat, so that in a 



