394 RESPIRATION 



which, as we know, are generally accompanied with the develop- 

 ment of heat, lose this property in the animal body ? This 

 much is established and placed beyond all doubt by the 

 labours of the most trustworthy observers, that the chemical 

 movements in the living body are more than sufficient to explain 

 the animal heat, and particularly that the process of oxidation 

 which is carried on through the respiration yields by far the most 

 important contribution to its excitation. Attempts have been 

 made to ascribe to the nervous system a share in the production 

 of heat, but, as we have already observed in vol. i., p. If, we 

 cannot form a conception of the nervous system in a state of 

 action without chemical changes occurring in it. Any one may 

 observe the depression of temperature that ensues in parts in 

 which the connexion between the nerves and the central nervous 

 system has been interrupted ; and we are well acquainted with the 

 recent experiments of certain French physiologists, who, after 

 dividing the sympathetic at a certain spot, have found the animal 

 heat, at definite parts, considerably higher than the ordinary tem- 

 perature, an observation which I have myself had occasion to 

 make ; and while we do not overlook the difficulties which oppose an 

 explanation of such phenomena in a special case, we must regard 

 every view as unscientific, and therefore incorrect, which would 

 refer the origin of animal heat, although only partially, to any other 

 than chemico-physical forces. 



If, however, the chemical theory of heat, as it has been gene- 

 rally understood, is open to objection, it seems to us that it can only 

 arise from its having been regarded less as the consequence than 

 as the object of all, or, at any rate, of most of the chemical move- 

 ments in the organism. Animal heat has, perhaps, been brought 

 too prominently forward in the consideration of the metamorphosis 

 of animal matter, so that it may almost have appeared as if a great 

 number of the animal processes were accomplished solely for the 

 purpose of generating heat in the living body. When we inquire 

 into the objects accomplished in the organism, animal heat acquires 

 a special significance from the fact, that most of the higher animals, 

 however they may otherwise differ, are endowed with a power of 

 compensation, which is so carefully adapted to each, that even the 

 most different external or internal relations are scarcely able to 

 produce the slightest fluctuations of temperature. The conclusion 

 which we might be led to draw from this fact, in reference to the 

 importance of animal heat for the vital functions, is certainly some- 



