344 PHILOSOPHY OF ZOOLOGY. 
to have been first stated by Fourcroy, and afterwards es- 
tablished by the author of the article Blood, i Rre’s Cy- 
clopeedia, and by the late Dr Gorpon of Edinburgh *. 
Previous to coagulation, if the atmospheric pressure be 
removed from the blood in an air-pump, a considerable 
quantity of air bubbles is disengaged, as was first clearly 
established by the experiment of Darwin}. Vocer deter- 
mined this air to be carbonic acid}; and Branpe found that 
two cubic inches were disengaged from every ounce of 
blood, and that the quantity was the same in arterial and 
venous blood ||. Even during spontaneous coagulation, 
Mr Bauer found the blood, when confined in a glass tube, 
to give out a considerable quantity of carbome acid §. It 
appears, likewise, from his observations, in company with 
Sir Everarp Home, that when a drop of blood is placed 
on a watch-elass, in the field of a microscope, the following 
changes may be perceived. ‘ The first thing,” (he says,) 
*¢ that happened, was the formation of a film on the surface, 
that part beginning to coagulate sooner than the rest. In 
about five minutes, something was seen to be disengaged © 
in different parts of the coagulum, beginning to shew itself 
where the greatest number of globules were collected ; and, 
from thence, passing in every direction, with considerable 
rapidity, through the serum, but not at all interfermg with 
the globules themselves, which had all discharged their co- 
louring matter ; wherever this extricated matter was carried, 
a net-work immediately formed, anastomosing with itself, on 
every side, through every part of the coagulum 4.” 
Are we to conclude from these statements, that carbonic 
acid exists in a gaseous state im the blood? The exper- 


* Annals of Phil. vol. iv. p. 139. + Phil. Trans. 1774, p. 344. 
+ Annals of Phil. vol. vii. p. 56. || Phil. Trans. 1818, p. 181. 
¥ Ibtd. | Ibid. p. 182. 
