vi FORM AND FUNCTION 99 
make an effort to resist them. In man the ordinary 
temperature is 98° and a fraction; a slight rise above 
this indicates fever, and a slight decline below it shows 
a failing of the bodily powers. When in health, the 
body can be exposed to enormous heat without itself 
growing appreciably warmer. The sensation of heat 
comes when great effort is required to keep the normal 
temperature. In the hottest room in Turkish baths 
the thermometer sometimes rises to 230° F., and some 
bathers remain there as long as 20 minutes. But this 
is far below the record. Doctors Fordyce and Blayden 
were able to remain some time in a chamber heated to 
260° F. I have been told that a man who earned his 
living by feats of this kind, found himself compelled to 
rush precipitately from a heated oven because some one, 
whowas more scientific than kind, had placed a can of hot 
water inone corner. Every one knows how oppressive 
the heat of a hothouse is. The heat of the vapour 
baths in Russia is said sometimes to rise to 116° F., 
but between this and 260° there is a great gulf. We 
have in this a hint as to one method of keeping down 
temperature—viz., by evaporation. Perspiration, or 
rather the evaporation, to which it gives rise, lowers 
the temperature of the body. When the air around is 
so damp that evaporation is slow, even moderate heat 
is oppressive. When through long exposure to a burn- 
ing sun, all the available moisture in the body has been 
exhausted, there results a feverish heat and an uncon- 
trollable thirst. Under these circumstances, a private 
soldier will not stop, to use his pocket-filter, if he 
happens to have been supplied with one, but will gulp 
down the most poisonous filth, though he knows it to 
H 2 
