119 



venal blood, received into a vessel, acquired a scar- 

 let colour by exposure to the air : that if this sur- 

 face was removed, the subjacent one was soon chan- 

 ged to the same colour : that if the cake of blood, 

 after being allowed to settle in the vessel, was in- 

 verted, its exterior and upper surface speedily also 

 assumed a florid hue : and, lastly, that if venal blood 

 was shaken in a vessel, so that the air thoroughly 

 intermixed with it, it became entirely florid *. These 

 opinions were afterwards held by Sig. Fracassati and 

 Dr Slare, the latter of whom observes, that the 

 blood thrown up by a rupture of the capillary ves- 

 sels of the lungs, is frothy and of a scarlet colour ; 

 the first of which effects he attributes to the inter- 

 mixture of air, and the latter to its tinging power f. 

 Mr Hewson employed similar arguments to prove, 

 that the florid colour, acquired by venal blood on 

 exposure, was produced by the contact of the air : 

 and, by injecting air into the jugular vein of a rab- 

 bit, he found that it there also rendered the blood 

 florid J. M. Cigna not only confirmed the forego- 

 ing facts, but proved also that the change of co- 

 lour in this fluid did not take place when the blood 

 was covered with oil or placed in vacuo ; and Dr 

 Priestley ascertained, that not only by common air, 

 but more especially by oxygen gas, this florid colour 

 was produced on the black crassamentum of blood (|. 



* Tract, de Corde, p. 178. An. 1669. 

 f Lowthorpe's Abrid. Phil. Trans, vol. Hi. p. 235. 

 J Hewson on the Blood, p. 9. 

 '] Priestley on Air, vol. iii. p. 66. 

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