ix] Doctrines of Respiration. 251 



1775, and hydrogen was first made definite and clear by 

 Cavendish in 1781. 



Thus in 1785 hydrogen was well known to Lavoisier, and he 

 was able to draw from the quantitative comparison of which I 

 have just been speaking the following important conclusion : 



" Besides the part converted into carbonic acid a portion 

 " of the inspired vital air does not issue as it enters. There 

 " results therefore one of two things ; this part either unites 

 "with the blood or combines (in the lungs) with a portion of 

 " hydrogen to form water." 



Had Lavoisier stopped here we should have been able to 

 say not only that he had in a most masterly manner solved the 

 general problem of respiration, but that every jot and tittle of 

 his work remained true and good for all time since his day. 

 He was however a little later on led into a false path. In 1790 

 he published in conjunction with the physiologist Sequin a 

 memoir on "The Transpiration of Animals." In that memoir 

 the authors give a luminous though brief exposition of the new 

 views which had been reached of the chemistry of the body. 

 They explain how digestion supplies the blood with the 

 material for combustion, with, carbon and hydrogen, how that 

 material undergoes combustion, is oxidized by the respiratory 

 process, thus giving forth heat, and how the products of that 

 combustion, water and carbonic acid, are got rid of through 

 the skin and lungs. They clearly recognize that part only of 

 the water thus thrown off comes from the oxidation of 

 hydrogen, indeed a small part only, the rest being merely 

 the water which serves as the vehicle of the solid food. The 

 exposition is quite a modern one save in one point. In the 

 discussion on the oxidation of respiration there occurs this 

 remarkable sentence, "one must know in the first place that 

 " there transudes into the bronchi a humour which is secreted 

 " from the blood and which is principally composed of carbon 

 "and hydrogen." 



The view put forward is that the oxidation of the carbon 

 and hydrogen supplied by the food takes place within the lungs, 

 in the tubes of the lungs, as the oxidation of a hydrocarbonous 

 fluid secreted into the tubes. 



Now Lavoisier was no anatomist, was not indeed a 



