1864.] 



of the Colouring Matter of the Blood. 



363 



salt, the change of colour is plainly due to a deoxidation of the cruorine. 

 On the other hand, Magnus removed as much as 10 or 12 per cent, by 

 volume of oxygen from arterialized blood by shaking the blood with car- 

 bonic acid. If, as we have reason to believe, this oxygen was for the most 

 part chemically combined, it follows that carbonic acid act s as if it were a 

 reducing agent. We are led to regard the change of colour not as a direct 

 effect of the presence of carbonic acid, but a consequence of the removal 

 of oxygen. There is this difference between carbonic acid and the real re^ 

 ducing agents, that the former no longer acts on a dilute and comparatively 

 pure solution of scarlet cruorine, while the latter act just as before. 



If even in the case of blood exposed to an atmosphere of carbonic acid 

 we are not to attribute the change of colour to the direct presence of the 

 gas, much less should we attempt to account for the darker colour of 

 venous than arterial blood by the small additional percentage of carbonic 

 acid which the former contains. The ascertained properties of cruorine 

 furnish us with a ready explanation, namely that it is due to a partial re- 

 duction of scarlet cruorine in supplying the wants of the system. 



20. I am indebted to Dr. Akin for calHng my attention to a very in- 

 teresting pamphlet by A. Schmidt on the existence of ozone in the blood*. 

 The author uses throtighout the language of the ozone theory. If by 

 ozone be meant the substance, be it allotropic oxygen or teroxide of hy- 

 drogen, which is formed by electric discharges in air, there is absolutely 

 nothing to prove its existence in blood ; for all attempts to obtain an oxi- 

 dizing gas from blood failed. But if by ozone be merely meant oxygen in 

 any such state, of combination or otherwise, as to be capable of producing 

 certain oxidizing effects, such as turning guaiacum blue, the experiments of 

 Schmidt have completely established its existence, and have connected it, 

 too, with the colouring matter. Now in cruorine we have a substance ad- 

 mitting of easy oxidation and reduction ; and connecting this with Schmidt's 

 results, we may infer that scarlet cruorine is not merely a greedy absorber 

 and a carrier of oxygen, but also an oxidizing agent, and that it is by its 

 means that the substances which enter the blood from the food, setting 

 aside those which are either assimilated or excreted by the kidneys, are 

 reduced to the ultimate forms of carbonic acid and water, as if they had 

 been burnt in oxygen. 



21. In illustration of the functions of cruorine, I would refer, in conclu- 

 sion, to the experiment mentioned in § 10. As the purple cruorine in the 

 solution was oxidized almost instantaneously on being presented with free 

 oxygen by shaking with air, while the tin-salt remained in an unoxidized 

 state, so the purple cruorine of the veins is oxidized during the time, brief 

 though it may be, during which it is exposed to air in the lungs, while 

 the substances derived from the food may have little disposition to combine 

 with free oxygen. As the scarlet cruorine is gradually reduced, oxidizing 

 thereby a portion of the tin-salt, so part of the scarlet cruorine is gradually 



* Ueber Ozon im Blute. Dorpat, 1862. 



