§32 PHILOSOPHICAL TRANSACTIONS. [aNNO 1779. 



the bladder. Having tlius ascertained that the bladders do not in any manner 

 contribute to render the inflammable air extracted from metals better in its na- 

 ture, there remained no other way of ascertaining Mr. Scheel's experiments, 

 and of understanding why I had been able to breathe it eleven times, than by 

 supposing that the air of the lungs, which can never be thoroughly emptied, by 

 being mixed with the inflammable air, alters it, &c. It is well known, -that in 

 an ordinary expiration about 35 cubic inches of air are expelled from the lungs. 

 In a very violent expiration, following a natural inspiration, the air expelled may 

 amount to 6o cubic inches. These 40 inches of pulmonary air are mixed with 

 the inflammable air, and are expelled from the lungs in proportion to the remain- 

 ing air that is breathed after the lungs have been thoroughly emptied. In the 

 experiment above related, of the 3 inspirations made into the inflammable air, 

 it may be easily supposed that '20 inches or more of pulmonaiy air were joined 

 with the inflammable air, and entered into the bladder. This pulmonary air, 

 though it is itself partly phlogisticated, is however diminished by nitrous air; 

 and when it stands in the bladder it is nearly equal to -"^ of the inflammable air 

 of the bladder breathed 3 times; hence this lost JO parts by the mixture of 

 nitrous air. 



This explanation, which it is necessary to adopt after having exploded all the 

 other hypotheses, is very analogous to the above related experiment of the 

 smaller bladder filled with inflammable air which was breathed 1 1 times succes- 

 sively. This air was breathed after a natural expiration, so that thei-e still re- 

 mained in the lungs about 75 inches of common air. These 75 inches of pul- 

 monary air, together with the 80 inches of inflammable air, were mixed together 

 during the 1 1 inspirations and expirations ; hence the air of the bladder was a 

 mixture of nearly equal portions of inflammable and common air ; and accord- 

 ingly, when tried with the nitrous air, it was found to be much better (though 

 it had been breathed 1 1 times) than the air of the large bladder breathed 3 times 

 only, after the lungs had been emptied as much as possible. 



AH the other experiments that I have made in confirmation of this hypothesis 

 seem universally to favour it. If a guinea pig is introduced into a receiver con- 

 taining 400 cubic inches of inflammable air, or a small bird into only 50 inches 

 of it, and they be left in it till they are dead, that air afterwards will not be sen- 

 sibly diminished by nitrous air; but if a much larger animal be introduced into 

 the 400 inches of inflammable air, or a small animal into a few cubic inches of 

 that air, then it will be found to be sensibly diminished by nitrous air ; and this 

 diminution will be greater as the animal is larger in proportion to the (juantity of 

 inflammable air. A larger animal imparts a greater quantity of its pulmonary 

 air to the inflammable air ; and the inflammable air will be found joined to a 

 quantity of pulmonary air, which is so much the less as the animal is smaller. » 



