24 1 Analyjis of the- Air. 



by the fum of all the veficles in the lungs, 

 viz. ioo cubick inches, will produce 60000 

 fquare inches ; one third of which muft be 

 deducted, to make an allowance for the ab- 

 fence of two fides in each little veficular 

 cube, that there might be a free communi- 

 cation among them for the air to pal's to 

 and fro ; fo there remain 40000 fquare 

 inches for the fum of the furface of all the 

 veficles. 



And the Bronchia containing 41 cubick 

 inches, fuppofing them at a medium to be 

 cylinders of -~ of an inch diameter, their 

 furface will be 1635 fquare inches, which 

 added to the furface of the veficles, makes 

 the fum of the furface of the whole lungs 

 to be 41635 fquare inches, or 289 fquare 

 feet, which is equal to 19 times the furface 

 of a man's body, which at a medium is com- 

 puted to be equal to 15 fquare feet. 



I have not had an opportunity to take in 

 the fame manner the capacity and dimen- 

 fions of human lungs; the bulk of which 

 Dr. James Keill, in his Tentamina Medico- 

 phxfica, p. 80. found to be equal to 226 cu- 

 bick inches. Whence he eftimated the fum 

 of the furface of the veficles to be 21906 

 fquare inches. But the bulk of human 



lungs 



