EDWARDS AND PROUT. 553 



reports, that arterial contains nearly the same 

 proportion of carbonic acid as venous blood, but 

 the former a little more oxygen and nitrogen. 

 The truth is, that if carbonic acid were formed 

 in the systemic capillaries, (as maintained by 

 Edwards, Miiller, Dr. Prout, and others,) they 

 ought to have a higher temperature than the 

 lungs, for the obvious reason, that whenever 

 oxygen unites with carbon caloric is evolved, 

 whether during ordinary combustion, fermenta- 

 tion, or respiration. But that the temperature of 

 arterial blood is reduced, instead of being aug- 

 mented in the systemic capillaries, is evident 

 from the fact, that on returning to the right side 

 of the heart, it is found to have lost from 1 to 3 

 of caloric, together with its bright florid hue, and 

 power of maintaining the actions of life, just as 

 the steam of an engine loses its elastic force and 

 the power of moving the piston, after under- 

 going a reduction of temperature. 



That venous is converted into arterial blood 

 during its passage through the lungs, was long 

 ago proved by the experiments of Lower, Mayo, 

 Hewson, Hunter, Goodwin, and Bichat, who, in 

 various species of animals, observed it to pass 

 from the right side of the heart, through the 

 pulmonary artery, of a dark hue, and return by 

 the pulmonary veins to the left ventricle, of a 

 bright florid complexion. It must not, however, 

 be supposed that the vital properties of the blood 

 are essentially connected with its colour, which 



