ACCOMMODATION FOR VARYING TEMPERATURES. 449 



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 18C., is moderately warm; 

 25-28C., hot; 

 above 28, very hot. 



Water, 



at 18C., is cold; 

 from 18-29C., cool; 



,, 29-35 -5 C., warm; 



,, 37 '5 and above, hot. 



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 45'5C. (dangerous to 

 life!); the hands may be plunged into water at 50'5C., but not at 

 5r65C., while at 60 violent pain is produced. 



A person may remain for eight minutes in air heated to 99*95- 

 127C., and a temperature of 132C. has been borne for ten minutes 

 (Tillett, 1763). The body-temperature rises only to 38'6-38'9 

 (Fordyce, Blagden, 1774). This depends upon the air being a bad 

 conductor, and thus it gives less heat to the body than water would do. 

 Farther, 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 much 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 60C., the rectal temperature rises to 40-7-41'6 C. (Barthels, 

 Jiirgensen, Krishaber). A person may work continuously in air at 

 31C. which is almost saturated with moisture (Stapff). 



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

 normal temperature rises 1C. in 1 hour, and in 1 J hours about 2C. 

 (Liebermeister). A gradual increase of the temperature from 38*6 to 

 40'2C. causes the axillary temperature to rise to 39'0C. within fifteen 



minutes. 



29 



