RESPIRATION. 145 



own ? Men have been known to remain several minutes in 

 an atmosphere heated above the boiling-point of water, and 

 yet the temperature of their own bodies was not greatly ele- 

 vated. Those who labor in foundries and glass-works are 

 habitually subjected to very high degrees of temperature, 

 but they do not suffer in health more than thosie engaged 

 in many other occupations. 



50. The regulation of the temperature of the body is 

 effected by means of perspiration, and by its evaporation. 

 So long as the skin acts freely and the air freely absorbs 

 the moisture, the heat of the body does not increase, for 

 whenever evaporation takes place, it is attended by the 

 abstraction of heat that is, the part becomes relatively 

 colder. This may be tested by moistening some part of 

 the surface with cologne, ether, or other volatile liquid, 

 and then causing it to evaporate rapidly by fanning. The 

 principle that evaporation produces cold has been in- 

 geniously and practically employed, in the manufacture 

 of ice, by means of freezing machines. 



51. Spontaneous Combustion. Is it possible that 

 the temperature of the living body can be so increased, 

 that its tissues will burn spontaneously ? From time to 

 time, cases have been reported in which, by some mysteri- 

 ous means, considerable portions of the human body have 

 been consumed, apparently by fire, the victim being found 

 dead, or incapable of explaining the occurrence. Hence, 

 the theory has been current that, under certain condi- 

 tions, the tissues of the body might become self-ignited ; 

 and the fact that this so-called spontaneous combustion 

 has ordinarily taken place in those who had been addicted 

 to the use of alcoholic drinks, has given a color of proba- 

 bility to the opinion. It has been supposed that the flesh 

 of these unfortunate persons becoming saturated with the 

 inflammable properties of the alcohol thus taken into the 



&O. The regulation of the temperature of the body. Give the explanation. 

 51) 52. State what is said of spontaneous combustion. 



