REGULATION OF HEAT PRODUCTION. 



863 



show a condition of marked polypnea (rapid breathing) the ap- 

 parent object of which is to augment the loss of heat from the 

 body. 



Regulation of Heat Production. Heat production is varied 

 in the body by increasing or decreasing the physiological oxida- 

 tions. This end is effected in part voluntarily by muscular exercise 

 or by taking more food. Muscular contractions are attended by 

 a marked liberation of heat and it is a part of everyone's experience 

 that by work or muscular activity the effect of outside cold may be 

 counteracted. In the case of food the body burns promptly most 

 of the material of a daily diet. By increasing the diet in cold 

 weather provision is made for the greater supply of heat required. 

 In normal individuals this regulation is not, strictly speaking, 

 voluntary. Outside cold is most effective in stimulating the appe- 

 tite and thus leading us to increase the diet. In this, as in other 

 respects, the appetite serves to control the amount of food in pro- 

 portion to the needs of the body. The purely involuntary control 

 of heat production consists of an involuntary reflex upon muscu- 

 lar metabolism and possibly in the existence of a special set of heat 

 centers and heat nerves. With regard to the first effect we have 

 the striking experiments quoted by Pfliiger,* according to which a 

 rabbit paralyzed by large doses of curare is no longer able to main- 

 tain its body temperature when the outside temperature is changed. 

 The rabbit behaves, in fact, like a cold-blooded animal. In the 

 calorimeter it shows a marked loss of heat production, and its 

 temperature may be made to go up and down with the outside 

 temperature. The same result may be obtained by section of all 

 the motor nerves, that is, section of the spinal cord in the upper 

 cervical region. Rubner has shown by calorimetric experiments 

 upon animals that although the body temperature, as we know, 

 may remain constant when the outside temperature is changed, 

 the heat production is increased as the outside temperature is 

 lowered. This fact is well shown by the following table, compiled 

 by Rubner, from experiments made upon a fasting guinea-pig :f 



From to about 35 C. the animal's body temperature remained 



*Pfliiger "Archiv f. die gesammte Physiologic, " 18, 255, 1878. 

 t Taken from Lusk, loc. dt. 



