572 INDUCTION. 



Difference, since flesh completely dried and kept in a 

 dry atmosphere does not putrefy, as we see in the case 

 of dried provisions, and human bodies in very dry 

 climates. A deductive explanation of this same law 

 results from Liebig's speculations. The putrefaction 

 of animal and other azotised bodies is a chemical 

 process, by which they are gradually dissipated in a 

 gaseous form, chiefly in that of carbonic acid and 

 ammonia ; now to convert the carbon of the animal 

 substance into carbonic acid requires oxygen, and to 

 convert the azote into ammonia requires hydrogen, 

 which are the elements of water. The extreme rapidity 

 of the putrefaction of azotised substances, compared 

 with the gradual decay of non -azotised bodies (such 

 as wood and the like) by the action of oxygen alone, 

 is explained by Liebig from the general law that 

 substances are much more easily decomposed by the 

 action of two different affinities upon two of their 

 elements, than by the action of only one. 



The purgative effect of salts with alkaline bases, 

 when administered in concentrated solutions, is 

 explained by Liebig from the two following principles : 

 Animal tissues (such as the stomach) do not absorb 

 concentrated solutions of alkaline salts ; and such 

 solutions do dissolve the solids contained in the intes- 

 tines. The simpler laws into which the complex Jaw 

 is here resolved, are the second of the two foregoing 

 principles combined with a third, namely, that the 

 peristaltic contraction acts easily upon substances in a 

 state of solution. The negative general proposition, 

 that animal substances do not absorb these salts, con- 

 tributes to the explanation by accounting for the 

 absence of a counteracting cause, namely, absorp- 

 tion by the stomach, which in the case of other 



