6 PHILOSOPHY OF ZOOLOGY. 
gulated. Internally, however, there is no rest. From the 
period that the existence of the plant or animal commences, 
to the day of dissolution, there is no stationary point. In- 
crease and decay succeed by turns. Youth follows infan- 
cy, and maturity precedes age. It is thus with the mushroom 
and the oak,—with the mite and the elephant,—life and 
death being common to all of them. 
III. Integument distinctive of Organized Bodies,—The 
substance of a stone or a crystal, is the sameat the sur- 
face and the centre. Minerals possess no covering to 
defend them from external injuries, and preserve their 
form. When they increase, it is by the addition of mat- 
ter to their surface; when they decrease, it is by the ab- 
straction of the exterior particles. But organized bodies 
are enveloped in a covering which differs in structure from 
the parts within, which defends those parts from the ac- 
tion of external agents, and which is susceptible of exten- 
sion and contraction. The increase of size is produced by 
the addition of particles to the interior, and an enlarge- 
ment of this integument. A diminution of size takes place 
from the removal of particles from the imterior, and a con- 
sequent contraction of the covering. 
_ Were it necessary, many characters besides those which 
have been enumerated, might be exhibited, as distinguish- 
ing the inorganic from the organized kingdom. The indi- 
viduals belongmg to the former do not require nourish- 
ment and a suitable temperature, neither do they possess 
a circulating system. Animals and vegetables, on the 
other hand, stand in need of a supply of food and air, and 
a suitable temperature, for the continuance of their exis- 
tence, and are nourished by particles prepared in appro- 
priate organs, and conveyed by peculiar vessels. Inorga- 
