AND ANIMAL LIFE. 177 



the blood. It will undergo this change before it 

 is inspired, which will lessen the quantity re- 

 ceived, and the internal warmth of the chest will 

 also tend to carry this change still farther. So we 

 observe that two causes are in operation, both of 

 which will diminish the usual proportion of air 

 acting on the blood ; and, moreover, this diminu* 

 tion will be in the direct ratio to the increase of tem- 

 perature, retarding its influence, not by the gener- 

 ation of cold, but by setting limits to the generation 

 of heat, 



CXCVII. CRAWFORD endeavoured to shew, 

 by direct experiment, " that when an animal is 

 placed in a heated medium, the sanguineous 

 fluid during each revolution is less impregnated 

 with the inflammable principle; for the venous 

 blood, in these circumstances, becomes gradually 

 paler in its colour, till at length it acquires nearly 

 the appearance of the arterial? The experi- 

 ments which he instituted, for the purpose of 

 proving this point, are far from being satisfac~ 

 tory. 



An animal was confined in a vessel containing 

 atmospheric air, which was at one time surround- 

 ed by water at 55, for 42 minutes, and at ano- 

 ther by water at 104, for the same period. At 

 the termination of the experiment, the air in the 

 former was found to be only one-fourth as pure 



* CRAWFORD, Experiments and Observations upon Animal 

 Heat, &c, p. 387. 



M 



