290. EESULTS OF PUTREFACTION. 



sulphuretted hydrogen, &c. ; Decay, a slow process 

 of oxidation, almost analogous to combustion, differ- 

 ing from putrefaction in being dependent on the pre- 

 sence of free oxygen or air. This change is always 

 accompanied by the evolution of heat; Mouldering, 

 a change intermediate between putrefaction and 

 decay, taking place in organic matters exposed to 

 the action of water, but not to that of air. 



766. Organic manures consist of mixtures of vari- 

 ous organic substances in a state of putrefaction or 

 decay. The more changeable substances at once 

 enter into putrefaction, sometimes communicating 

 their own state to those which are less changeable, 

 sometimes only inducing decay in them ; thus, for 

 example, urine soon putrefies by itself, and, if mixed 

 with straw, it gradually causes the latter to heat and 

 decay. 



767. Whilst describing the different varieties of 

 organic matter, attention has constantly been drawn 

 to the results produced by their putrefaction. It 

 has been repeatedly stated that the substances formed 

 by the putrefaction of organic matter are water, car- 

 bonic acid, and ammonia. The nature and rapidity 

 of the change is, however, greatly modified by cir- 

 cumstances. 



768. Organic matter containing nitrogen changes 

 far more rapidly than that not containing this ele- 

 ment (350). It might have been supposed that under 

 such circumstances the nitrogen would be given off 

 in a free and uncombined state ; it is therefore re- 



