24:8 ON THE COLOUR OF THE BLOOD. 



errors of former ages, and rendered plain and easy the path to 

 the temple of science. — The ancient philosophers, seem to have 

 entertained very incorrect ideas of the cause of the red colour of 

 the blood, and I believe it was very little understood, before the 

 celebrated Priestley Lavoisier and Scheele discovered oxigi- 

 nous gas, or vital air; since that memorable period, many and 

 various have been the opinions adopted on the vermilion colour 

 of the blood, and each one has had its votaries. 



It has been proved by a variety of experiments made by 

 these eminent chemists, that atmospheric air, is a mixture of 

 oxigene and azotic gases, in the proportion of twenty-live parts 

 of the former, and seventy-five parts of the latter. Priestley, 

 Cigna, Hewson, Thouvenel and Beccaria, have made many 

 experiments on the blood, and have all united in the opi- 

 nion that its vermilion colour, should be attributed to the ab- 

 sorption of oxigene, by the blood, in its passage through the 

 lungs during respiration. This doctrine sanctioned by such 

 imposing names, influenced for a long time, physiologists and 

 chemists to adopt it as the only true philosophy, which had 

 ever been promulgated. The great Darwin, whose imagina- 

 tion was too transcendant to be imprisoned within the bounds 

 of ordinary men, instituted a new theory of the vermilion co- 

 lour of the blood, partly founded upon the foregoing princi- 

 ples, which nevertheless is infinitely more fanciful than phi- 

 losophical; for he observes, "that during respiration, the blood 

 imbibes the vital part of the air, called oxigene, through the 

 membranes of the lungs; and that hence respiration may be 

 aptly compared to a slow combustion. — As in combustion the 

 oxigene of the atmosphere unites with some phlogistic or in- 

 flammable body, and forms an acid (as in the production of 

 the vitriolic acid from sulphur, or carbonic acid from charcoal) 

 giving out at the same time a quantity of the matter of heat, 

 so in respiration, the oxigene of the air unites with the phlo- 

 gistic part of the blood, and probably produces phosphoric or 

 animal acid, changing the coiour of the blood from a dark to 

 a bright red." 



Chaptal in his treatise on the blood, remarks that " the co- 

 lour of the blood has been attributed to iron; that the blood 



