120 



97. In effecting these remarkable alterations in 

 the colour of the blood, the air itself, at the same 

 time, suffers material changes. Dr Priestley found, 

 that in Jwenty-four hours oxygen gas was so far de- 

 praved by being in contact with venal blood, that 

 one measure of it and two of nitrous gas occupied 

 the space of a measure and a half, whereas, at the 

 beginning of the experiment, they occupied the space 

 of no more than half a measure *. Dr Goodwyn 

 confined venal blood under a jar of oxygen gas in- 

 verted in mercury, and repeatedly observed that the 

 change of colour was always very sudden, and, after 

 several minutes, the mercury ascended two or three 

 lines ; from which he concluded that a small portion 

 of the air had disappeared |. The precise change, 

 however, which the air underwent, seems first to 

 have been observed by Dr Girtanner, who placed 

 six ounces of venal blood in a jar of oxygen gas in- 

 verted in mercury : the blood presently assumed a 

 florid colour : the air was somewhat diminished in 

 bulk, and contained a portion of carbonic acid, 

 which was attracted by lime-water J. Dr Bostock 

 observes also, that a diminution of oxygen and 

 production of carbonic acid take place when a piece 

 of crassamentum is placed in a jar filled with oxy- 

 gen gas ||. The same production of carbonic acid 

 we found to occur when blood is placed in contact 



* Priestley on Air, vol. iii. p. 75. 

 f Goodwyn's Essay, p. 61. 



f Memoirs on Irritability in Bcddoes' Obs. on Calculus, &c. 

 p. 219. 



!| On Respiration, p. 227. 



