124 RELATIONS OF MAN WITH EXTERNAL NATURE 



the tendency of all of which may be expressed by the term oxidation, 

 oxygen, derived from without, being largely concerned in those changes, 

 and the ultimate products being, when such changes are completed, 

 chiefly water, carbonic acid, ammonia, and sulphates. The whole of 

 these changes are analytic. In plants, the inorganic constituents of 

 the food water, carbonic acid, ammonia, and sulphates once ab- 

 sorbed, also undergo, under the influence of light, many changes; the 

 characteristic of which is deoxidation, oxygen being given off in the pro- 

 cess, which may be characterized as synthetic. Plants, therefore, build 

 up from the dead or inorganic world, the organic materials of their 

 own fabric, and also those which alone can be converted into the sub- 

 stance of animals; whilst these latter restore to the inorganic world 

 the chemical elements which have passed in succession through the 

 living tissues of both plants and animals. In this way, indeed, the 

 balance between the two great subdivisions of the organic kingdom is 

 maintained, and the continued existence of both insured. The germi- 

 nating embryos, and the flowering parts of plants, however, give off 

 carbonic acid; and so do all the parts of plants, during the absence of 

 light; not, as may be suggested, in consequence of a process of oxida- 

 tion, but because the carbonic acid, which then enters them as food, 

 is no longer decomposed. It is also generally alleged that parasitic 

 and other fungi absorb carbonic acid and give off oxygen, both during 

 day and night ; but, as regards the daytime, this is doubted by some. 



In conclusion, the broad distinctions between animals and plants, 

 consist in the possession, by the former, of true sensibility, conscious- 

 ness, and volition ; in the further possession of a stomach ; in their in- 

 ability to form albuminoid compounds, or other organic substances, 

 directly from inorganic materials ; and lastly, in their absorption of 

 oxygen, and evolution of carbonic acid. On the other hand, plants 

 are destitute of volition, consciousness, and true sensation ; have no 

 stomach ; can form albuminoid and other organic compounds from in- 

 organic matter; absorb and fix carbon, and give off oxygen. Lastly, 

 it may be mentioned that, as a rule, animals, in accordance with their 

 higher functions, possess not only more complex organs, but a much 

 larger number of component tissues. 



The form and structure of any microscopic organized body, will 

 usually suffice to decide its proper position in the one or the other of 

 the two organic kingdoms of nature, provided only that it be in its 

 fully developed condition ; but in regard to germs, whether ova or 

 spores, it is difficult, and sometimes impossible, to arrive at a conclu- 

 sion. 



RELATIONS OF THE ORGANIC WITH THE INORGANIC KINGDOM OF 

 NATURE, OR OF ANIMALS AND PLANTS WITH MINERALS. 



Plants, and animals, including man, which compose the organic 

 world, are distinguished from the inorganic world by their manifesta- 

 tion of "life." The Linnaean definition, "Lapides crescunt, Vegetabilia 

 crescunt et vivunt, Animalia crescunt, vivunt et sentiunt," i. e., u Stones 

 grow, Plants grow and live, Animals grow, live, and feel," also ex- 



