VOL. XXX.] PHILOSOPHICAL TRANSACTIONS. 343 



above marked, was easily found. Having repeated the experiment 10 times, 

 and adding together the several quantities found each time, their lOth part, or 

 the mean bulk of water poured into the vessel, was found equal to 35 cubic 

 inches ; which is the bulk of air contained in the bladder, and adding about a 

 12th part more, or 3 cubic inches, by reason of the condensation of the air by 

 the coldness of the water, it being in the winter time, there arose 38 cubic 

 inches. Besides, there must somewhat be added, both on account of the pres- 

 sure of the water on the bladder, and also on account of the vapour, emitted 

 with the breath, and turned into moisture, which must necessarily happen both 

 from the coldness of the water and from the contact of the moistened bladder. 

 Therefore I estimated the quantity of air emitted in gentle expiration in 3 

 seconds of time, in round numbers, at 40 cubic inches. In the strongest expi- 

 ration I emitted 125 cubic inches in one second of time. And by this sort of 

 expiration, which, with a violent straining, I had continued till almost choaked, 

 I emitted 220 cubic inches. Whence it appears, to mention this by the bye, 

 that there remains much more air in the breast than is emitted by one mean 

 expiration. 



If therefore /be put = 2 feet; 9 = 40 cubic inches; a = 125 cubic inches; 

 t = Z"', T = 1''; the specific gravity of air to that of water, as 1 to tOOO; a 

 cubic foot of water = 1000 ounces avoirdupois; the mean motion of the air, 

 expired from the lungs, will be equal to the motion of 4 scruples 9 grains 

 weight, which runs over 1 inch in a second of time, or equal to the motion of 

 14- grain weight, which in the same time may run over the length of 5 feet 7 

 inches; which is the velocity of the air emitted through the larynx, supposing 

 the section of the larynx = -i^ of a square inch. 



The greatest motion of the air emitted from the breast is equal to the motion 

 of about \\ oz. weight, which runs over 1 inch in a second of time; or equal 

 to the motion of 14- gr. weight, which runs over 52 feet in the same time; 

 which is the velocity of the air emitted through the larynx in the strongest 

 expiration. 



Cor. 1 . — Given the quantity of air and length of the wind-pipe, the motion 

 of the air is in the inverse ratio of the time of expiration. 



Cor. 2. — Given the bulk of the air and the time, the motion will be in the 

 direct ratio of the length. 



Cor. 3. — Given the length and time, the motion will be as the quantity of 

 the air. 



Cor. 4. — Given the motion and quantity of air, the length will be in the direct 

 ratio of the time. 



