CHAPTER XYI. 



OF THE PHYSIOLOGICAL OFFICE OF RESPIRATION. 



IT is necessary to distinguish between the fundamental biological 

 fact of the absorption of oxygen, which is one of the first con- 

 ditions of nutrition, and the physiological function properly so 

 called, which is simply the physiological process employed to. 

 render this absorption possible and easy. The absorption of 

 oxygen is a general fact ; every organised being absorbs oxygen 

 under penalty of death ; this is true as regards the most humble 

 vegetal and animal organisms, as well as the highest. It is true 

 of every living being in all the stages of its existence. William 

 Edwards and Colin 1 have shown that seeds do not germinate in a 

 vacuum, and it was sufficient for Reaumur to cover an egg with an 

 impenetrable varnish to prevent the embryon from developing. 2 

 But respiration, properly so called, only and truly exists in those 

 cases where a special branchial, trachean, or pulmonary apparatus 

 is the means of furnishing with respirable air the entire organ- 

 ism, and of exhaling those gases which are hurtful to or useless 

 for the maintenance of life. 



Whatever may be the diversity of the organological pro- 

 cesses, the object of all respiratory apparatus is to bring the 

 capillary vessels containing blood more or less vitiated by nutri- 

 tion into as easy contact as possible with the atmosphere. If 

 we were to employ the language of the ancient natural philoso- 



1 Comptes Eendus de V Academic des Sciences, 1838. 



2 Ibid., year 1735. 



