252 The Rise of the Modem [lect. 



physiologist, and in his other writings does not venture into 

 physiological as distinct from chemical hypotheses. One can- 

 not help suspecting that he was led astray into this wrong 

 hypothesis by his more distinctly physiological comrade. 

 However it be, the idea of the hydrocarbonous fluid laid hold 

 of men's minds, and was accepted as an integral part of the 

 new doctrine of respiration : accepted, but not by all. In 

 the following year, 1791, Hassenfratz, a chemist of some 

 reputation, who had been assistant to Lavoisier, and was now 

 assistant to the mathematician Lagrange, in a paper in the 

 Annates de Chimie, 'On the combination of oxygen with the 

 carbon and the hydrogen of the blood ; on the solution of the 

 oxygen in the blood ; and on the manner in which caloric is 

 set free,' expounds the following view of respiration as put 

 forward by Lagrange : " M. Lagrange reflecting that if all the 

 "heat which is distributed in the animal economy was set free 

 " in the lungs, the temperature of the lungs would therefore 

 " necessarily be raised so much that one would have reason to 

 " fear they would be destroyed, and that moreover were the 

 " temperature of the lungs so much higher than that of other 

 "parts, this fact could hardly have escaped observation, con- 

 " eluded accordingly with great probability that the heat of the 

 " animal economy was set free not in the lungs alone, but in all 

 " parts of the body where the blood circulated." 



Lagrange supposed therefore that the blood in passing 

 through the lungs dissolved the oxygen of the inspired air, and 

 that this dissolved oxygen was carried away by the blood into 

 the arteries and thence into the veins, and that " in the course 

 "of the journey of the blood the oxygen little by little quitted 

 " the condition of solution in order to combine in part with the 

 "carbon and in part with the hydrogen of the blood, and so to 

 " form carbonic acid and water, which are set free from the 

 " venous blood so soon as this leaves the right side of the heart 

 " to enter the lungs." And Hassenfratz relates, in support of 

 Lagrange's view, experiments of his own, on the changes in 

 colour of blood when exposed to oxygen on the one hand, and 

 to carbonic acid on the other; but these, which are in the 

 main repetitions of Priestley's earlier experiments, do not 

 amount to much. 



