220 PMYTOCHEMY. 



animal matters, again, and in those juices of plants wliich ap- 

 proach to an animal nature, another decomposition takes 

 place, during which hydrogen and azote })rincipally are disen- 

 gaged. This change is called Putrefaction. Both of these 

 changes afford products, which did not previously exist as 

 such in the organic body, and from which, therefore, we can- 

 not conclude, with any certainty, respecting the component 

 parts of the living substance. 



343. 



The second peculiarity of the composition of organic bodies, 

 is, that it is more or less independent on the inorganic bo- 

 dies that may happen to be present. It cannot be denied, 

 indeed, that the comjX)sition of the earth and water, by 

 which plants are nourished, has a considerable influence on 

 their ingredients, and that at all times plants, and especially 

 tlie lower orders of them, partake more than animals of the 

 composition of the substances by which they are surround- 

 ed. In general, however, it is a law of nature, that every 

 organic body forms its own ingredients out of the elemen- 

 tary materials which surround it ; and that the quantity of 

 lime contained in plants which grow in pure sand, or whicli 

 spring amidst granite, is not less than the quantity of the 

 same material contained in those plants which grow on a cal- 

 careous soil. In a few instances, some compound matters 

 seem to pass unchanged into plants and the presence of com- 

 mon salt and of soda in plants which grow on the sea-shore or 

 on calcareous soils, is as undeniable as the passage of metallic 

 substances, and of many odorous and colouring matters, into 

 the blood and secreted juices of the animal body. On the 

 other hand, it is estabhshed, that neither odorous nor colour- 

 ing matters pass unchanged into the un wounded roots of 

 plants ; and that we cannot accomplish the absorption of co- 

 loured fluids by these parts in any other way, but by cutting 

 the twigs, so as to bring these fluids into direct contact with 

 the sap-tubes. 



