626 EVOLUTION OF HEAT, LIGHT, AND ELECTRICITY. 



to account for the total amount of Heat generated by a warm-blooded animal 

 in a given time ; this assertion being founded upon the experimental results 

 obtained by M. Dulong. It has been shown by Prof. Liebig, however, that the 

 estimates originally made require correction for the true calorific equivalents of 

 carbon and hydrogen ; and that, this correction having been made, the heat 

 produced by the combustion of the Carbon which is contained in the carbonic 

 acid expired, and by the combustion of such a proportion of the Hydrogen con- 

 tained in the exhaled water as may be fairly considered to have undergone 

 oxygenation within the system ( 569), proves to be adequate to compensate 

 for that which would be dissipated by the evaporation of all the water trans- 

 pired from the skin and lungs, and also to maintain the temperature of the 

 body itself in an atmosphere of ordinary coolness. 1 And to the combustion 

 heat of carbon and hydrogen, we should also add that of those relatively minute 

 quantities of Phosphorus and Sulphur, which also undergo oxidation within the 

 system, whereby a small additional amount of heat must be generated. Through 

 whatever diversity of combinations or successive stages of oxidation these ele- 

 ments respectively pass, in their progress to complete or final oxidation, it may 

 be regarded as an indisputable fact, that they give out precisely the same amount 

 of heat in the whole, as if they had undergone the most rapid combustion in pure 

 oxygen ; and thus we may look to almost every molecular change in the body, 

 although pre-eminently to those which are concerned in the disintegration of its 

 textures and in the elimination of their products by Respiration, as participating 

 in the function of Calorification. 



662. It cannot be denied, however, that there are certain phenomena which 

 seem at first sight to be completely opposed to this doctrine, and which can 

 scarcely be explained in accordance with it, save by a considerable modification 

 in our usual ideas. The class of facts to which reference is here made, are 

 those which indicate that the Nervous system has a very important concern in 

 the process, and that it is, in fact, one of the immediate instruments in the 

 development of heat. Thus it was experimentally shown by Sir B. Brodie, 2 

 that when the Brain is cut off from the spinal cord, or its functions are sus- 

 pended by the agency of a narcotic, and artificial respiration is practised, so that 

 the circulation is maintained, the body not only loses heat rapidly, but may 

 even cool more rapidly than the body of an animal similarly treated, but in 

 which artificial respiration is not performed. Now it is certainly true, as was 

 subsequently pointed out by Drs. Wilson Philip and Hastings, 3 and by Dr. C. 

 Williams, 4 that the effect of the artificial performance of respiration depends in 

 some degree upon the mode in which it is accomplished; for that if, as in most 

 of Sir B. Brodie's experiments, the insufflation be repeated 30 times or more 

 in a minute, the cooling effect of the air thus introduced is greater than the 

 warming effect of the imperfect respiratory change to which it becomes subser- 

 vient; whilst if the insufflation be repeated only 12 times in a minute, the 

 cooling of the body, as compared with that of a body in which the circulation 

 is not thus maintained, is retarded, instead of being accelerated. But still it is 

 evident from Sir B. Brodie's experiments, that the withdrawal of the influence 

 of the Encephalon has a positively depressing effect upon the Calorific function ; 

 for the rapid fall of temperature took place even in cases in which the amount 

 of carbonic acid exhaled during the performance of artificial respiration, was 

 fully equal to the normal quantity; and the subsequent experiments of MM. 



1 See P. of Liebig's "Animal Chemistry," 3d edit., p. 44. 



2 "Philosophical Transactions," 1811, 1812; and "Physiological Researches." 



3 See Dr. Wilson Philip's "Experimental Inquiry into the Laws of the Vital Functions," 

 3d edit., p. 180. 



"Ediub. Med.-Chir. Trans.," vol. ii. p. 192. 



