PLYMOUTH INSTITUTION. 33 



November 19th — Mr. Swain's Lecture on Respiration. 



In this lecture, Mr. Swain reminded the Society of the constitu- 

 tion of the atmospheric air, and observed that its oxygen was the 

 active ingredient, nitrogen being a mere diluent. He spoke of 

 the imperfection of our analytical investigations of air, since we 

 were unable to detect any difference between the atmosphere of 

 an infected hospital, and that taken from the summit of Mount 

 Blanc. 



He divided his remarks into two sections : — the first related to 

 the changes effected on the air by respiration ; and the second, to 

 the changes produced by the air upon the blood. Mr. S. then 

 described, by a reference to his diagrams, the lungs and wind-pipe, 

 with the whole economy of the two functions, circulation and 

 respiration, exhibiting the connection which exists between the 

 two. 



He then by experiment proved, that carbonic acid gas was ex- 

 pired from the lungs ; and stated, that it was computed, that 

 eleven ounces of pure charcoal or carbon was evolved every 

 twenty-four hours of our existence: this carbon was derived 

 from the blood sent into the lungs, to be divested of its super- 

 abundant quantity. The blood sent into the lungs, was nearly 

 black ; having been acted upon by the air, it assumed a brilliant 

 scarlet color, and became again fit to circulate through the body. 

 Opinions were divided, as to whether the changes effected on 

 the air and on the blood, took place, simply in the lungs, or 

 whether they were effected during the course of the circulation. 

 The weight of evidence seemed to prove, that the atmospheric 

 air was actually absorbed by the blood in the lungs, and that it 

 was replaced by air containing carbonic acid gas ; that, during 

 the circulation through the body, the changes produced were 

 effected, thus rendering the function infinitely beyond a mere 

 chemical operation, and endowing it with all the importance of 

 vitality. 



During the lecture, Mr. S. performed experiments, to show 

 that carbon was actually evolved from the lungs. He said that 

 the principal difficulty felt by the uninitiated was, in conceiving 

 how solid charcoal could be dissolved in gas. There were some 

 striking analogial experiments which would show the possibility 

 of the fact ; several clear liquids when united were shown to con- 

 tain a vast quantity of solid matter ; and a portion of charcoal 



VOL. VII.— -1836. E 



