250 Transactions of tee American Institute. 



SCIENTIFIC LECTURE-IV. 



ON AIE A]S^D RESPIRATION. 



By Prof. J. C. Draper, op tiik College op the City op New York. 



Judge Daly, Yice-President of the Institute, introduced the lec- 

 turer, who spoke as follows : 



Ladies a^td Gentlemen. — "We have met this evening to discuss a 

 subject of vital importance to every living creature. In whatever 

 light we may view it we can do but very imperfect justice to so suggest- 

 ive a theme in one lecture ; but since time is our inexorable master, 

 in this [as in all other things, it only remains for us to accomplish 

 what we may in the brief allotted space of a single hour. 



Atmospheric air bears a three-fold relation to respiration, for we 

 may consider their connection from a mechanical, chemical or physio- 

 logical standpoint. It is more especially to the second and third 

 of these that we call your attention to-night, since they have a prac- 

 tical value that is self evident. 



In past times this impalpable, invisible, gaseous envelope of our 

 earth was regarded as an elementary body, but more exact methods 

 of research have demonstrated that it is not simple but very compo- 

 site, containing two classes of ingredients : 1. Those which do 

 not vary in their relative proportion to each other and to tlie whole 

 mass ; 2. Those which are so variable that the proportions change 

 with every succeeding hour, and, we might almost say, with every 

 succeeding moment. 



To place these components in the clearest light, we have arranged 

 them in a tabular form, a glance at which will show how rapidly we 

 must proceed to perform a mere tithe of the work tliat is before us : 



Invariable. 



Nitrogen. 

 Oxygen. 



Variable. 



Carbonic acid. Ammonia. 



Carbonic oxyd. Vapor of water. 



Ozone. Sulphuretted hydrogen. 



Nitric acid. Corpuscles and various vapors. 



