108 



89. From a review, therefore, of all the facts and 

 experiments above stated, we venture to draw the 

 following conclusions, as approaching nearest to the 

 truth. First, then, according to Mr Davy, the lungs 

 contain, after a forced expiration, a bulk of air equal 

 to about 41 cubic inches ; and according to the 

 same author and Dr Goodwyn, they contain, after 

 a natural expiration, from 109 to 118 cubic inches: 

 therefore the state of forced is to that of natural ex- 

 piration as 41 to 118. Secondly, according to Dr 

 Menzies, 40 cubic inches of air are received into the 

 lungs at each ordinary inspiration : therefore the 

 state of natural expiration to that of natural inspira- 

 tion will be as 118 to 158. Mr Davy found like- 

 wise, that by a forced expiration after a forced in- 

 spiration, he could expel from his lungs 19O cubic 

 inches of air, and Dr Menzies often found it to a- 

 mount to 200 inches : therefore the state of great- 

 est exhaustion of the lungs is to that of greatest re- 

 pletion, as 41 to 231. But the 41 cubic inches of 

 air, when inspired at temperature 55, occupied a 

 bulk equal only to 32 ; and therefore, by the same 

 rule of proportion, 19O cubic inches, inspired at the 

 same temperature, will be increased to 241.5 : con- 

 sequently, the greatest diminution of the capacity of 

 the chest to its greatest expansion will be as 41 to 

 241, in the case of Mr Davy. But these numbers 

 must be considered as indicating proportions only, 

 the absolute quantities being different in different 

 persons *. These facts decidedly shew how much 



* At the time of making these experiments, Mr Davy states 



