30 



known. We have only been able to ascertain, 

 that the dark blood turns red ; and we conclude, 

 from the quality of the respired air, that the dark 

 blood has lost a portion of its carborv ; but whether 

 any of the immediate constituent parts of the 

 blood have become altered in their qualities, is a 

 subject not yet examined, although it is probable, 

 that, by a chemical analysis, very interesting- re- 

 sults might be derived from the comparison be- 

 tween venous and arterial bk>od. It has been ge- 

 nerally believed, that every part of the blood is 

 influenced by the air; that it absorbs oxygene,, 

 and exhales carbonic acid gas ; but this is not the 

 case* Bloody in which the colouring* matter is 

 still contained, absorbs oxygene gas very quickly,, 

 when out of the body and shaken in atmospheric 

 air; it also- retains at the sam-e time some p&rt of 

 the carbonic acid, thereby produced ; on the other 

 hand, serum, when destitute of colouring matter, 

 does not change the atmospheric air before it be- 

 gins to putrify. 



The principal effect on the air is produced by 

 the colouring matter, and as this matter does not 

 penetrate any of the re-producing, and but few 

 of the secreting capillary vessels, it appears as if 

 the principal object of the colouring matter, were 



