280 PRINCIPLES OF BOTANY, ETE€. 
§ 274. : 
Krom all those circumstances together, which we 
have hitherto explained, compared with the observa- 
tions which we intend still to make, we are enabled 
‘o make some general conclusions with regard to 
The air-vessels, (§ 235), no doubt perform - 
‘ost Important functions in plants. Their won- 
derful structure alone, (fig. 282), were we not to 
attend, to what we have said. of them in the preceding 
page, would lead us to conclude, that they must be 
destined to answer very important purposes. No- 
bedy, however, has as yet offered a decided opinion 
with regard to their operations. We shall therefore 
now make an attempt to explain their use. 
That vegetables have hfe, was proved, (§ 224, 
226), betore. If we now compare this vegetable 
life with that of animals, we will, sensation except- 
ed, find very little difference. We observe that ani- 
mals are provided with one or more apertures, by 
which they inhale air, and without which life ceases. 
We find that they take in food by one aperture, which 
food, according to the difference of animals, must pass 
through variously-shaped canals; that they prepare 
from it those particles which are fit to support life, 
and which are assimilated by the vital power. Fur- 
ther, we see that the remnants of the alimentary 
mass, as soon as they cease to contain any thing’ ser- 
viceable for the machine, are thrown out. Noanimal 
can subsist without those processes, none grow and 
thrive. Does not, therefore, nature follow a similar 
plan 
