1 8 INSTABILITY OF ORGANIC COMPOUNDS. 



formed out of comparatively few elements ; secondly, their 

 great proneness to decomposition. For it is a general 

 rule, that the greater the number of equivalents or atoms 

 of an element that enter into the formation of an atom of 

 a compound, the less is the stability of that compound. 

 Thus, for example, among the various oxides of lead and 

 other metals, the least stable in composition are those in 

 which each equivalent has the largest number of equiva- 

 lents of oxygen. So, water, composed of one equivalent 

 of oxygen and one of hydrogen, is not changed by any 

 slight force; but peroxide of hydrogen, which has two 

 equivalents of oxygen to one of hydrogen, is among the 

 substances most easily decomposed. 



The instability, on this ground, belonging to the more 

 peculiar animal organic compounds, is augmented, ist, by 

 their containing nitrogen, which, among all the elements, 

 may be called the least decided in its affinities, that which 

 maintains with least tenacity its combinations with other 

 elements ; and, 2ndly, by the quantity of water which, in 

 their natural mode of existence, is combined with them, 

 and the presence of which furnishes a most favourable 

 condition for the decomposition of nitrogenous compounds. 

 Such, indeed, is the instability of animal compounds, 

 arising from these several peculiarities in their constitu- 

 tion, that, in dead and moist animal matter, no more is 

 requisite for the occurrence of decomposition than the 

 presence of atmospheric air and a moderate temperature ; 

 conditions so commonly present, that the decomposition of 

 dead animal bodies appears to be, and is generally called, 

 spontaneous. The modes of such decomposition vary ac- 

 cording to the nature of the original compound, the tem- 

 perature, the access of oxygen, the presence of microscopic 

 organisms, and other circumstances, and constitute the 

 several processes of decay and putrefaction ; in the results 

 of which processes the only general rule seems' to be, that 

 the several elements of the original compound finally unite 



