92 DISTINCTIVE CHARACTERS OF LIVING ORGANISMS, 
gelatine can only be formed in the animal body by a me 
morphosis of the albumen which it derives from the Plant. 
The peculiar mode in which the elements of these substa 
are held together, renders them very prone to decompeatigll 
so that Organized bodies, when no longer alive, rapidly pas 
into decay, unless they are secluded from the contact o 
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 o: 
the system as fast as they are generated within it. I 
essentially consists in the resolution of the four principa 
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 
organic world the original materials of Organized fabrics, im 
the very forms from which those materials were first derived 
by the agency of the growing Plant. (See Vucrt. Puysiot.) 
5. It is, however, by their peculiar actions, that livin 
Organisms are most completely: differentiated from the iner 
bodies of which the Mineral kingdom is composed. Ther 
can be no doubt that of many of the changes which tak 
place during the life of an Organized being, a large proportio: 
(especially in the Animal kingdom) are effected by the di 
agency of physical and chemical forces; and there is 
reason to believe that these forces have any other operatior 
im the living body, than they would have oué of it unde 
similar circumstances. Thus the propulsion of the blood by 
the heart, through the large vessels, is a purely mechani¢ 
phenomenon ; as is also the movement of the limbs by th 
lever-action of the forces brought to bear on their bone 
So, again, the digestive operations which take place in 
stomach are of a purely chemical nature ; and the interchang 
of gases between the air and the blood, which takes place i 
the act of respiration, must be regarded in the same light. 
But after every possible allowance has been made for th 
operation of physical and chemical forces in the living o 
ganism, there still remain a large number of phenomef 
which cannot be in the least explained by them, and whi¢ 
must be regarded as the result of an agency that differs fromi)}} 
these as they differ from each other ; and this agency, which}. 
