22 DISTINCTIVE CHARACTERS OF LIVING ORGANISMS. 
gelatine can only be formed in the animal body by a meta¬ 
morphosis of the albumen which it derives from the Plant. 
The peculiar mode in which the elements of these substances 
are held together, renders them very prone to decomposition ; 
so that Organized bodies, when no longer alive, rapidly pass 
into decay, unless they are secluded from the contact of 
oxygen, or are kept at a very low temperature. Such decay, 
however, is continually taking place during life, and would 
make itself obvious if its products were not carried out of 
the system as fast as they are generated within it. It 
essentially consists in the resolution of the four principal 
components of organic compounds—carbon, hydrogen, oxy¬ 
gen, and nitrogen, in combination with oxygen drawn from 
the atmosphere—into the three binary compounds, water, 
carbonic acid, and ammonia, which thus restore to the In¬ 
organic world the original materials of Organized fabrics, in 
the very forms from which those materials were first derived 
by the agency of the growing Plant. (See Veget. Physiol.) 
5. It is, however, by their peculiar actions , that living 
Organisms are most completely differentiated from the inert 
bodies of which the Mineral kingdom is composed. There 
can be no doubt that of many of the changes which take 
place during the life of an Organized being, a large proportion 
(especially in the Animal kingdom) are effected by the direct 
agency of physical and chemical forces; and there is no 
reason to believe that these forces have any other operation 
in the living body, than they would have out of it under 
similar circumstances. Thus the propulsion of the blood by 
the heart, through the large vessels, is a purely mechanical 
phenomenon; as is also the movement of the limbs by the 
lever-action of the forces brought to bear on their bones. 
So, again, the digestive operations which take place in the 
stomach are of a purely chemical, nature; and the interchange 
of gases between the air and the blood, which takes place in 
the act of respiration, must be regarded in the same light.— 
But after every possible allowance has been made for the 
operation of physical and chemical forces in the living or¬ 
ganism, there still remain a large number of phenomena 
which cannot be in the least explained by them, and which 
must be regarded as the result of an agency that differs from 
these as they differ from each other; and this agency, which 
