24 ANIMAL MECHANISM. 



intense causes of cooling, which may lie compensated by a 

 suitable variation of heat. Bunseii's regulator solves this 

 problem satisfactorily, by regulating the supply of gas which 

 serves as a combustible, augmenting it if the inclosed air 

 tends to grow cold, diminishing it in the opposite case. 



In the animal economy, two orders of influences tend in- 

 cessantly to cause variation of temperature in its production 

 and in its expenditure. Causes of loss of temperature exist, 

 as in the instance just mentioned. The temperature of the 

 surrounding air, against which our clothing protects us more 

 or less efficiently, on the one hand, and the more or less 

 easy evaporation by means of cutaneous perspiration, accord- 

 ing to the hygrometrical state of the atmosphere on the 

 other ; the action of the wind, or of air-currents ; the tem- 

 perature of the baths which we take, all these different 

 causes tend to increase or diminish the waste of heat to 

 which the body is subject. To these influences must be added 

 those of the hot or cold food which we eat ; of the hot or 

 cold air introduced into our lungs by respiration, &c. All 

 these constitute in general the causes of loss of heat. 



Auother variable element in the establishment of the 

 animal temperature is the production of heat which takes 

 place in the interior of the organism, and which, as well as 

 its loss, varies under numerous influences. The aliments of 

 which we partake, act, through their nature and quantity, on 

 this production of internal heat ; the activity of the glands 

 causes a discharge of caloric ; and the case is the same with 

 respect to muscular action, which cannot be produced without 

 the heating of the muscle. 



It is true that within certain limits our senses warn us to 

 restrict the production of heat, or to promote it, according as 

 external influences diminish or augment its waste. Thus, 

 the amount of food taken varies "with climate, so that the en- 

 force! sobriety of the dweller in hot countries has no raison 

 d'etre in cold ones. Obligatory idleness during the heat 

 of the day under a burning sky is one manner of diminishing 

 the production of heat; the Northmen, on the contrary, en- 

 deavour to compensate, by muscular activity, for tho cold to 

 \\ hich they are subjected. 



