888 Transactions of the American Institute. 



would be burned up, and naught left but its ashes ; and when vitality 

 ceases to antagonize or resist its action, we return to the dust from 

 which we sprung. 



Then breatliing is not for the purpose of purifying the blood, but 

 to break down the tissues of the body, and remove them under the 

 direction and control of the vital principle. In all animal tissues 

 tliere is work performed wliich has a tendency to wear out and render 

 unfit for service parts of themselves, parts or molecules that have 

 lost their vitality, and these worn out molecules become the food for 

 oxygen. These worn out atoms are for tlie most part hydrogen and 

 carbon. The oxygen seizes upon them and converts them, by thus 

 uniting with them, into carbonic acid and water; or, using another 

 figure, the oxj^gen may be regarded as scavenger boats, which enter 

 the lungs, pass into the blood, and are carried into every part of the 

 body, where they are loaded with these worn out elements, carbon 

 and liydrogen. With these loads they return through the veins to 

 the lungs, and pass out into the air in the form of carbonic acid and 

 vapor of water. They are now taken up by the leaves of the trees, 

 miloaded, the carbon and hydrogen entering into and becoming a 

 part of the tree, while the unloaded scavenger boats (oxygen) are 

 returned to the atmosphere to repeat the process. Verily, then, 

 " the leaves are for the healing of the nations." This, then, is the 

 ofiice of respiration, to remove the worn out tiss^ies of the lady. 



Kow, if the air is more or less saturated with this carbonic acid, 

 some of these loaded barges, when we inhale a breath of air, will 

 enter too. The demand of the tissues is for vehicles to convey away 

 the waste products, and the demand is imperative ; and, though the 

 loaded barges go at the call of the suffering tissues, they cannot 

 remove any of the material, for they are already completely loaded. 

 Two atoms of oxygen can take l>ut one of Citrbon, and, therefore, 

 they but obstruct and block up the way, and thus produce disorder 

 and disturbance — disease. 



Now, tliere must always be a small amount of carbonic acid in the 

 atmosphere, because it is continually being emitted by the whole ani- 

 mal kingdom, and as a product of combustion and decay. Yet, by 

 the peculiar law of gaseous diffusions, it is so completely dift'used 

 through, or mingled with, the atmosphere, that it amounts to only 

 1-2500 of its weight. 



As the specific gravity of carbonic acid is considerably greater than 

 that of the air, we?e it uot for this gaseous diffusion it would settle to 



