333 



§ 4. Chemical Changes effected by Respiration. 



We have next to direct our attention to the che- 

 mical offices which respiration performs in the 

 animal economy. It is only of late years that 

 we may be said to have obtained any accurate 

 knowledge as to the real nature of this important 

 function ; and there is perhaps no branch' of 

 physiology which exhibits in its history a more 

 humiliating picture of the wide sea of error in 

 which the human intellect is prone to lose itself, 

 when the path of philosophical induction is 

 abandoned, than the multitude of wild and 

 visionary hypotheses, devoid of all solid founda- 

 tion, and perplexed by the most inconsistent rea- 

 sonings, which formerly prevailed with regard to 

 the objects and the processes of respiration. To 

 give an account, or even a brief enumeration of 

 these theories, now sufficiently exploded, would 

 be incompatible wdth the purpose to which I 

 must confine myself in this treatise.* I shall 



* For an account of the history of the various chemical 

 theories which have prevailed on this interesting department of 

 Physiology, I must refer to the " Essay on Respiration," by Dr. 

 Bostock, and also to the " Elementary System of Physiology," 

 by the same author, which latter work comprises the most com- 

 prehensive and accurate compendium of the science that has 

 yet appeared. 



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