INTROD.] DECOMPOSITION. LIFE. 13 



it need not excite surprise that a great variety of products results 

 from the decomposition of animal and vegetable matter. This de- 

 composition is of two kinds, which are distinguished by the names, 

 fermentation, and putrefaction. Liebig proposes to limit the former 

 term to the decomposition of substances devoid of nitrogen, and the 

 latter to that of azotised matters. The products of vegetable mat- 

 ter in fermentation, by the action of yeast, are carbonic acid and 

 alcohol ; those of azotised matters, whether animal or vegetable, 

 are carbonic acid, hydrogen, phosphuretted and carburetted hydro- 

 gen, hydrosulphuric acid, cyanogen, hydrocyanic acid, ammonia, 

 and lactic acid. 



Let us compare the characters of organized bodies, as described 

 in the preceding paragraphs, with those of inorganic substances. 



In form, in size, in duration, the contrast is most striking. The 

 inorganic matters are aeriform, liquid, or solid : they are prone to 

 assume the crystalline form, and to exhibit surfaces bounded by 

 right lines, and uniting to form angles. No distinction of parts, or 

 organs, is to be found in the mineral substance ; its minutest frag- 

 ment is in every respect of the same nature with the largest mass. 

 A portion of chalk, not weighing a drachm, contains particles of 

 the same form and size as those of the largest cliff on the sea-coast. 

 Inorganic substances, as compared with organic, are unlimited in 

 size and duration : they will continue for ages without augmentation 

 or waste, provided no mechanical violence nor chemical agent be 

 brought to act upon them. 



None of those internal actions or processes, which we described 

 in the organized body, occur in the unorganized one ; there is no 

 power of reproducing lost or injured parts, no growth, no excretion, 

 no generation. From age to age the mineral remains unchanged, 

 without motion, obedient to the common laws of matter, and unable 

 to resist them by any inherent power. 



Within the living organisms of the organic kingdom, on the con- 

 trary, are ceaseless motion and change. The absorption of the new 

 material, and the ejection of the old, comprise a continual succes- 

 sion of actions, in which the organised being is ever organizing and 

 disorganizing. This constant round of actions, which is the more 

 diversified as the organism is more complex, we call LIFE. There 

 is an apparent spontaneousness in these actions, which distinguishes 

 the mechanism of an animal or plant from the machines of human 

 construction. Yet the living organism is not the less dependent 

 for the continuance, nay, for the very existence of those actions, 

 upon the ordinary agencies of nature. Light, heat, the atmosphere, 



