608 FUNCTIONS OF ANIMALS. 



the respiration of animals.* He considered atmospherical air 

 as a mixture of oxygen and azotic gases. He showed that, during 

 respiration, the azotic portion of the air remained unchanged, 

 but the oxygen portion diminished, and the portion which dis- 

 appeared was replaced by carbonic acid gas. Thus he verified 

 the fact discovered by Black, and rectified the statements of 

 Priestley. Lavoisier considered respiration as a true combus- 

 tion. In the lungs, the carbon of the blood combined with the 

 oxygen of the air, and converted it into carbonic acid gas, just 

 as happens when charcoal is burnt. 



In the year 1788, an important treatise was published by Dr 

 Edmond Goodwyn, entitled On the connection of Life with Res- 

 piration.^ He endeavoured to determine the capacity of the 

 lungs, the quantity of air which they contain, and the volume 

 drawn in and emitted in ordinary respiration. But some of his 

 estimates of these seem to have far exceeded the true average 

 quantities. In the year 1790, appeared Dr Menzies's Tentamen 

 Inaugurate de Respiratione, originally printed as a thesis when he 

 graduated in Edinburgh, but afterwards, I believe, published in 

 an English dress. J He endeavoured to determine the capacity 

 of the lungs, the quantity of air drawn in and thrown out at 

 each respiration, and the volume of oxygen gas converted into 

 carbonic acid gas with more accuracy than had been done by 

 Goodwyn, though I doubt whether he was successful. The latest 

 experiments of Lavoisier and Seguin on respiration were pub- 

 lished by Seguin in the Memoirs of the French Academy for 

 1789, (p. 566.) 



I shall not continue this historical detail any farther. The 

 facts ascertained by Davy, Allen and Pepys, Prout, Berthollet, 

 &c., will be noticed as we proceed. 



The fluid respired by animals is common atmospherical air ; 

 and it has been ascertained by experiment, that no other gaseous 

 body with which we are acquainted can be substituted for it. All 

 the known gases have been tried ; but they all prove fatal to the 



* Mem. de 1' Academic des Sciences, 1777, p. 185. 



f It is said to have been written in consequence of a prize offered by the Hu- 

 mane Society for the best essay on the method of recovering persons apparent- 

 ly drowned. 



| But I have only seen the Latin thesis printed by Menzies when he gra- 

 duated at Edinburgh in 1790. 



A posthumous volume published after the abolition of the Academy. 



