10 RELATION BETWEEN ANIMATED FORMS AND THE ATMOSPHERE. 



present climates of the earth's surface and the animals that reside on it how abundant 

 is the proof that all are still under the control of physical agents ! Things being so, 

 and each species having its assigned spot, from which it does not wander, for many 

 ages the same inhabitants are found in the same places. They change as individuals 

 only : the old decline and die away, the young spring up in their stead. I do not 

 know whether, in taking these general reviews of the earth, we ought to have any re- 

 gard for individuals ; whether we ought to consider them as they come into existence 

 and exhibit the strength and vigour of youth, and the decrepitude and languor of old 

 age. Life and death are familiar to us, because as individuals we have a deep personal 

 interest in them ; but the cares of Nature are beyond a day. In the Drama of the Universe, 

 each actor performs his part, whether leading or obscure, and, though he may retire 

 from the scenes, the play goes forward to its catastrophe. Whether it be an individual 

 or a race, each, by the actions of its life, has given some turn to the general course of 

 events. In the undulations that circle on a quiet lake, each particle alternately rises 

 up and sinks into repose ; but that particle, minute as it was, that motion, small as it 

 might be, was absolutely necessary to keep up the onward motion of the waves. Under 

 this point of view, the destiny of each individual is connected with the destiny of the 

 world. 



30. With each breath that I have drawn since I came into the world, I have im- 

 pressed a change on the earth's atmosphere. One year with another I have removed 

 therefrom eight hundred pounds of oxygen gas, and have cast into it a much greater 

 weight of carbonic acid, made up of the detritus of atoms which have been dismissed 

 from the system as unfit for the continuance of life. It is the express function of the 

 act of respiration to produce this result. That carbon, thus given forth, was received 

 in the form of food, it sated the cravings of hunger, or gratified those animal pleasures 

 which depend on the sense of taste. Taken by appropriate apparatus from the stom- 

 ach, it passed into the circulation, and, grouped with other materials, it changed into 

 blood ; and now, by capillary attraction, aided by the action of the heart, it was car- 

 ried to every part of the body, and became a constituent of a living being a temporary 

 constituent only. As we have said, it is a vulgar error that the distinction between a 

 living and a dead body is in the circumstance that the former can maintain itself with- 

 out change, while the latter undergoes putrefactive decomposition. Both equally pu- 

 trefy, or, if there be a difference, the change goes on most quickly in a living system. 

 The true distinction rests in this, that a living body is accommodated with machinery 

 to remove the decomposing atoms, and hence the process is conducted in a regulated 

 way. A chemist looks upon life as made up of unceasing deaths. And those atoms 

 of carbon are removed because their life is over, and they pass, by the action of the 

 lungs, into the atmosphere as carbonic acid gas. 



31. But their function is not ended. There, it is true, they commingle with the 

 elements of the air, and are no longer fit to support the respiration of man. The ways 

 of Nature are marvellous. This gas, cast away by animal forms, serves now as food 

 for plants and trees. Under the influence of the solar beams, the leaves that have been 

 unfolded in spring, spreading their broad expansions to the air, commence the decompo- 



