552 HUNTER AND HASSENFRATZ. 



of animal temperature, the latter cannot be 

 " owing to the fixation or condensation of 

 oxygen in the blood, and the combinations into 

 which it enters in the circulation," as maintained 

 by Dr. Davy ; nor to " the combination of oxygen 

 with carbon in the systemic capillaries," as 

 supposed by many modern physiologists. 



Should it still be urged,, that the agitation of 

 venous blood with oxygen gives it the arterial 

 colour, I answer that sugar, nitrate of potass, 

 sulphate of soda, chloride of sodium, carbonate of 

 potass, sal ammoniac, and even carburetted hy- 

 drogen (accordingto Berzelius), produce the same 

 effect, but destroy its vitality, and power of coa- 

 gulating. Moreover, when arterial blood is with- 

 drawn from the system, it acquires the colour 

 and other properties of venous blood, without 

 either the loss or gain of ponderable matter. 

 For it was found by Hunter, that on tying the 

 carotid artery of a dog in two places, the blood 

 between the ligatures soon acquired the dark 

 venous hue; and by Hassenfratz, that when 

 confined in glass tubes, hermetically sealed, it 

 underwent the same change of colour as when 

 placed in vacua, hydrogen, nitrogen, carbonic 

 acid, or common air. Miiller admits, that as ar- 

 terial is converted into venous blood while passing 

 through the systemic capillaries, the former 

 ought to contain principally oxygen, and the 

 latter carbonic acid in solution. But we have 

 seen, from the experiments of Magnus which he 



