335 



with oxygen gas, in place of atmospheric air, were attended with the 

 like results, but in a more striking degree $ and tend therefore to 

 corroborate the views entertained by the author of the theory of re- 

 spiration. According to these views, it is neither in the lungs, nor 

 generally in the course of the circulation, but only during its passage 

 through the capillary system of vessels, that the blood undergoes the 

 change from arterial to venous ; a change consisting in the formation 

 of carbonic acid, by the addition of particles of carbon derived from 

 the solid textures of the body, and which had combined with the oxy- 

 gen supplied by the arterial blood : and it is by this combination that 

 heat is evolved, as well as a dark colour imparted to the blood. The 

 author ascribes, however, the bright red colour of arterial blood, not 

 to the action of oxygen, which is of itself completely inert as a co- 

 louring agent, but to that of the saline ingredients naturally contained 

 in healthy blood. On arriving at the lungs, the first change induced 

 on the blood is effected by the oxygen of the atmospheric air, and 

 consists in the removal of the carbonic acid, which had been the 

 source of the dark colour of the venous blood ; and the second con- 

 sists in the attraction by the blood of a portion of oxygen, which it 

 absorbs from the air, and which takes the place of the carbonic acid. 

 The peculiar texture of the lungs, and the elevation of temperature 

 in warm-blooded animals, concur in promoting the rapid production 

 of these changes. 



May 28, 1835. 



Sir BENJAMIN COLLINS BRODIE, Bart., Vice-President, in 



the Chair. 



A paper was in part read, entitled, " On the Influence of the Tri- 

 cuspid Valve of the Heart on the Circulation of the Blood." By 

 Thomas Wilkinson King, Esq., M.R.C.S. Communicated by Tho- 

 mas Bell, Esq., F.R.S. 



