334 ACCOMMODATION FOR VARYING TEMPERATURES. 



passive, and absorbed 30 grin. O per hour in a calorimeter, and produced 155 

 calories. When in the calorimeter he did work equal to 27,450 kilogramme- 

 metres, which was transferred beyond it; he absorbed 132 grm. O, and produced 

 only 251 calories. 



In estimating the work done, we must include only the heat-equivalent of the work transferred 

 beyond the bodv ; lifting weights, pushing anything, throwing a weight, and lifting the body, 

 are examples. In ordinary walking we must take into account that we overcome the resistance 

 of the air and the activity of the muscles. 



The organism is superior to a machine in as far as it can, from the same amount 

 of potential energy, produce more work in proportion to heat. Whilst the very 

 best steam-engine gives \ of the potential energy in the form of work, and f as 

 heat, the body produces 1 as work and 4 as heat. Chemical energy can never do 

 work alone, in a living or dead motor, without heat being formed at the same 

 time. 



218. ACCOMMODATION FOR VARYING TEMPERATURES. All sub- 

 stances which possess high conductivity for heat, when brought into contact with 

 the skin, appear to be very much colder or hotter than bad conductors of heat. 

 The reason of this is that these bodies abstract far more heat, or conduct more 

 heat than other bodies. Thus the water of a cool bath, being a better conductor 

 of heat, is always thought to be colder than air at the same temperature. In our 

 climate it appears to us that 



Air, at 18 C. is moderately warm ; Water, at 18 C. is cold ; 



,, at 25-28 C, hot ; ,, from 18-29 C, cool ; 



above 28, verv hot. ,, 29-35 C, warm ; 



,, ,, 37*5 and above, hot. 



Warm Media. As long as the temperature of the body is higher than that of 

 the surrounding medium, heat is given off, and that the more rapidly the better 

 the conducting power of the surrounding medium. As soon as the temperature of 

 the surrounding medium rises higher than the temperature of the body, the latter 

 absorbs heat, and it does so the more rapidly the better the conducting power of 

 the medium. Hence, hot water appears to be warmer than air at the same 

 temperature. A person may remain eight minutes in a bath at 45*5 C. 

 (dangerous to life ! ) ; the hands may be plunged into water at 50*5 C, but not at 

 51*65 C, while at 60 violent pain is produced. 



A person may remain for eight minutes in hot air at 127 C, and a temperature 

 of 132 C. has been borne for ten minutes, and yet the body temperature rises only to 

 38*6 or 38 '9. This depends upon the air being a bad conducter, and thus it gives 

 less heat to the body than water would do. Further, and what is more important, the 

 skin becomes covered with sweat, which evaporates and abstracts heat, while the 

 lungs also give off more watery vapour. The enormously increased heart-beats 

 over 160 and the dilated blood-vessels, enable the skin to obtain an ample supply 

 of blood for the formation and evaporation of sweat. In proportion as the secretion 

 of sweat diminishes, the body becomes unable to endure a hot atmosphere ; hence 

 it is that in air containing muck watery vapour a person cannot endure nearly so 

 high a temperature as in dry air, so that heat must accumulate in the body. In a 

 Turkish-vapour bath of 53 to 60 C, the rectal temperature rises to 40*7 or 41*6 

 C. A person may work continuously in air at 31 C. which is almost saturated with 

 moisture. 



If a person be placed in water at the temperature of the body, the normal 

 temperature rises 1 C. in one hour, and in \\ hour about 2 C. A gradual 

 increase of the temperature from 38-6 to 40*2 C. causes the axillary temperature 

 to rise to 39*0 within fifteen minutes. 



219. STORAGE OF HEAT. As the uniform temperature of the body, under 

 normal circumstances, is due to the reciprocal relation between the amount of heat 



