306 PHYSIOLOGY. 



supported by a few experiments of Mr. Brodie,(who kept up 

 artificial respiration in animals after cutting off their heads. 

 He found that, notwithstanding, the usual changes took 

 place in the blood, and in the air introduced into the lungs, 

 yet the temperature fell even faster than in another animal 

 killed at the same time, in which respiration wae not kept 

 UD.J This experiment, however, is not conclusive, as an ani- 

 mal may be cooled by forcing too much air into the lungs ; 

 and if less be introduced the heat may be preserved for some 

 time. 



9. Another theory is, that animal heat is generated in 

 the capillary system. /This is supported by the fact, that 

 some parts of the body are often hotter than others, as in 

 inflammation ; that it is always proportioned to the ener- 

 getic action of any organ, as the head becomes hotter by 

 hard study ; and; a glass of spirits excites a feeling of warmth 

 in the stomach./ 



10. ftt may be laid down as an axiom, or admitted truth, 

 that all movements among the particles 'of bodies which 

 cause a change of state, are attended with change of tem- 

 perature) This is the case in combustion, which is a 

 union of oxygen with the inflammable body, and the 

 production of carbonic acid ; and so also when two liquids 

 are mixed together, which chemically unite, heat is always 

 evolved. Now, in all the processes of nutrition, secretion, 

 digestion, respiration, &c., such changes are constantly 

 going on. In respiration, a part of the blood is thrown off 

 in a gaseous form, while a quantity of oxygen unites with 

 the remaining portion. This process, according to all the 

 known laws of caloric, must be attended with an elevation 

 of temperature. And this proves to be the fact. 



11. By the function of nutrition, fluids are changed into 

 solids ; and by absorption, solids are changed into .fluids ; by 

 secretion, new chemical compounds are formed out of a few 

 simple elements contained in the blood ; and by digestion, a 



