1864.] 



of the Colouring Matter of the Blood, 



361 



combined with some constituent of the blood. The latter and more natural 

 view seems for a time to have given place to the former in consequence of 

 the experiments of Magnus. Bat Liebig and others have since adduced 

 arguments to show that the oxygen absorbed is, mainly at least, chemically 

 combined, be it only in such a loose way, like a portion of the carbonic acid 

 in bicarbonate of soda, that it is capable of being expelled by indifferent 

 gases. It is known, too, that it is the red corpuscles in which the faculty 

 of absorbing oxygen mainly resides. 



Now it has been shown in this paper that we have in cruorine a substance 

 capable of undergoing reduction and oxidation, more especially oxidation, 

 so that if we may assume the presence of purple cruorine in venous blood, 

 we have all that is necessary to account for the absorption and chemical 

 combination of the inspired oxygen. 



16. It is stated by Hoppe that venous as well as arterial blood shows 

 the two bands which are characteristic of what has been called in this 

 paper scarlet cruorine. As the precautions taken to prevent the absorption 

 of oxygen are not mentioned, it seemed desirable to repeat the experiment, 

 which Dr. Harley and Dr. Sharpey have kindly done. A pipette adapted 

 to a syringe was filled with water which had been boiled and cooled without 

 exposure to the air, and the point having been introduced into the jugular 

 vein of a live dog, a little blood was drawn into the bulb. Without the 

 water the blood would have been too dark for spectral analysis. The 

 colour did not much differ from that of scarlet cruorine ; certainly it was 

 much nearer the scarlet than the purple substance. The spectrum showed 

 the bands of scarlet cruorine. 



This, however, does not by any means prove the absence of purple cruo- 

 rine, but only shows that the colouring matter present was chiefly scarlet 

 cruorine. Indeed the relative proportions of the two present in a mixture 

 of them with one another and with colourless substances, can be better 

 judged of by the tint than by the use of the prism. With the prism the 

 extreme sharpness of the bands of scarlet cruorine is apt to mislead, and 

 to induce the observer greatly to exaggerate the relative proportion of that 

 substance. 



Seeing then that the change of colour from arterial to venous blood as 

 far as it goes is in the direction of the change from scarlet to purple cruo- 

 rine, that scarlet cruorine is capable of reduction even in the cold by sub- 

 stances present in the blood (§ 9), and that the action of reducing agents 

 upon it is greatly assisted by warmth (§ 7), we have every reason to believe 

 that a portion of the cruorine present in venous blood exists in the state 

 of purple cruorine, and is reoxidized in passing through the lungs. 



1 7. That it is only a rather small proportion of the cruorine present in 

 venous blood which exists in the state of purple cruorine under normal 

 conditions of life and health, may be inferred, not only from the colour, 

 but directly from the results of tke most recent experiments *. Were it 



* Funk's Lehrbuch der Physiologic, 18G3, vol. i. § 108. 



