284 
NATURAL HISTORY. 
sion a compound of gluten, gelatine, albumen and magma, as also 
numerous insoluble ingredients. It holds in solution a portion of 
the nitrogen, hydrogen, and carbonic acid, and probably ammonia. 
In this, when in a state of putrefactive fermentation, a number of 
minute animalcules (called infusoria ) are detected by the aid of the 
microscope. To suppose that these animalcules are produced by the 
putried infusion, without the agency of eggs from parent animalcules, 
would be to admit equivocal generation , a theory too absurd and 
monstrous for any philosopher, much less a Christian, to admit for 
a moment; but the puzling question then presents itself whence did 
the eggs come ? 
To answer this question in a satisfactory manner to the minds of 
all enquirers, may be a matter of considerable difficulty; but I think 
our previous analytical investigation will lead to the following induc¬ 
tive reasoning:— 
As these animalcules are found in liquids only, and the species 
referred to in putrefactive infusion generally, and as all stagnant wa¬ 
ters which hold putrid vegetable matter in suspension afford some of 
them, I think we may conclude, that water is their native element, 
and putrid vegetable matter first their nidus, where they are hatched; 
and, perhaps, their first pabulum or food on their exclusion from the 
egg. I do not say their constant food, since the oxy-hydrogen mi¬ 
croscope clearly shows that they are cannibals, and devour each 
other. 
If, then, we consider the eggs to have been laid in the water, 
(though too small even for the most powerful glasses to detect) and 
only to require a proper nidus, pabulum, and temperature, to bring 
them to life, we have in the infusion in question all the conditions 
required, viz. gluten, gelatine, and magma, as nidus and pabulum, 
and the heat generated by the process of putrefactive fermentation; 
added to which we have the temperature of the atmosphere in the 
summer season, when they are most abundant. 
ARTICLE XIX.—INSECTS DESTRUCTIVE TO PLANTS, 
As enumerated by Mr. Main, in his excellent Practical Work,—“ Physiology of Plants,” 
Lately Published. 
Although it be impossible to particularise every species of insect 
which breed and prey on plants, a few of the more common and 
noxious may be mentioned, in order to show how the health of plants 
is injured, and their members distorted or destroyed by their depreda¬ 
tions. 
