235 ON 1HE COLOUR OF THE BLOOD. 



on the venous blood of animals, exposed to it, compared with 

 the effects produced on similar quantities of blood exposed to 

 atmospheric air; and also the effects produced on tbe blood of ani- 

 mals who have breathed the nitrous oxide gas, compared with the 

 blood of those who have breathed atmospheric air, support in a 

 very conclusive manner the doctrine 1 have adopted to explain the 

 red colour of the blood. — For he observes that 'nitrous oxide gas,' 

 is composed of oxigene 37 parts, and nitrogene 63 parts, — 

 " existing perhaps in the most intimate union which those sub- 

 stances are capable of assuming; for it is unalterable by those 

 bodies which are. capable of attracting oxigene from nitrous gas, 

 and nitrous acid at common temperatures."* — He exposed two 

 vials of venous blood, one to the nitrous oxide, and the other 

 to atmospheric air, and found that the coagulum of the blood ex- 

 posed to the nitrous oxide, was rendered darker and more pur- 

 ple, than the blood exposed to atmospheric air. — Also blood 

 drawn from two animals, one who had breathed the nitrous 

 oxide, and the other atmospheric air, and he found that the 

 blood of the two animals assumed difterent colours, corres- 

 ponding with the blood exposed to the two different gases, 

 mentioned in the above experiment. — Hence the inference is, 

 that the affinity between the oxigene and the nitrogene of the 

 nitrous oxide, is much stronger than the affinity between the 

 oxigene and the nitrogene of the atmospheric air; that the 

 temperature of the blood, together with the attraction of the 

 iron therein, being insufficient to disengage much oxigene 

 from the nitrous oxide, consequently less heat is evolved from 

 the partial decomposition of the nitrous oxide, than from at- 

 mospheric air in the process of respiration, therefore the iron 

 in the blood is only oxided in an inferior degree, which ac- 

 counts fur the fixation of the yiolet coloured ray, (the easiest 

 of refrangibility) and resolves the phenomenon of the purple 

 colour, the blood assumes from the effects of the nitrous oxide. 

 — " Likewise the blood altered by nitrous oxide gas, is capable 

 of being again rendered vermilion by exposure to common air, 

 qc to oxigene gas." 



• Sec Divy'i Chemical Retearchei. 



