THE BLOOD. 9 



air. After letting it rest a little, till the air should become 

 warm, I took off the ligature which separated the air from the 

 blood, and then gently mixed them, and I observed that the 

 venous blood assumed a more florid redness, where it was in 



blood when acted on by the air-pump did not acquire the arterial hue, 

 even when carbonic acid was abstracted ; and yet the florid tint was im- 

 parted to venous blood by agitating it with a mixture of oxygen and 

 carbonic acid gases, although the blood absorbed a much larger portion 

 of the latter than of the former gas. 



The results of these two last experiments, as Dr. Davy remarks, are 

 nowise reconcilable with the theory of Dr. Stevens, but perfectly in 

 accordance with the older views which he controverts. Dr. C. J. B. 

 Williams' 1 gives some experiments to prove that oxygen and the salts 

 produce the florid effect by causing the reflection of more light through 

 the colouring matter. Dr. Davy concludes that neutral salts brighten 

 the blood by separating the corpuscles, so that they reflect more light ; 

 and that water, acids, and other agents, darken the blood by altering 

 the form of tbe corpuscles and partially dissolving the colouring matter. 

 He remarks that hematozine is black only in mass, and red when re- 

 duced to powder, or viewed in a small portion by transmitted light. 



This exactly agrees with the conclusion of Dr. Wells,' that air and 

 neutral salts affect tbe blood just as bright vermilion is produced from 

 cinnabar by subjecting it to minute mechanical division. He proves by 

 an ingenious experiment, that the opacity of the blood and the reflection 

 of light from it are increased by neutral salts. Now, if the brightening 

 of the blood arise simply from the action of the agents on the colouring 

 matter, it should suffer the same change when separated from the cor- 

 puscles ; but this it does not ; for although Dr. Stevens states that the 

 salts strike a scarlet colour with the pure black hematozine,* this effect 

 did not occur in several trials which I made by treating a solution of 

 it either with oxygen, sugar, or neutral salts. The experience of Dr. 

 Davy with common salt, and of Dr. Wells with air and neutral salts, 

 was the same ; and Mulder 1 found that hematozine, separated from the 

 corpuscles, is not changed in colour either by oxygen, carbonic acid, or 

 protoxide of nitrogen. In all my experiments the red corpuscles were 

 reduced in size, both in breadth and thickness, by neutral salts, and in 

 a less degree by sugar and by oxygen ; while the first effect of water 

 and of carbonic acid was to swell the corpuscles and make them more 

 globular, though they became much smaller after the hematozine dis- 

 solved in the fluid. The observations of H. Nasse, Schultz, Henle, u and 

 of Mulder, T are in many respects similar. In short, it would appear 

 that it is simply to changes in the corpuscles and their state of aggre- 



> Lond. Med. Gaz. 1835, xvi, 788. Q Anatomic Generate, tr. par Jourdan, 

 r Phil. Trans. 1797, pp. 423-4, 418. t. i, pp. 461, 463, 471-2, 8vo, Paris, 



s Phil. Trans. 1835, p. 352. 1843. 



1 Chemistry of Veget. and Animal Phys. v Op. cit. p. 339 et seq. 

 Part ii,"p. 344. 



