188 THE LAWS OF ORGANIC 



they have been stated in xxi. as originating from 

 the diminished quantity of air within the chest ; 

 and it appears equally consistent to refer those 

 co-existent with great heat to the same physical 

 principle. If, therefore, the air is rarefied before 

 it is inspired, and if its general bulk be subse- 

 quently materially lessened; and if, in conjunction 

 with these two conditions, we consider, that the 

 quantify of air in the lungs indispensable to main- 

 tain the powers of life is very much rarefied by 

 an extensive and constant evolution of caloric, 

 we are enabled to appreciate the boundaries 

 which Nature has set to the generation of animal 

 heat. 



