THE VOLATILE PART OF PLANTS. 95 
In plants, the Protein Bodies occur in a variety of modi- 
fications, and though found in small proportion in all their 
parts, being everywhere necessary to growth, they are 
chiefly accumulated in the seeds, especially in those of 
the cereal and leguminous grains. 
The albuminoids, as we shall designate them, that oc- 
cur in plants, are so similar in many characters, are, in 
fact, so nearly identical with the albuminoids which con- 
stitute a large portion of every animal organism, that we 
may advantageously consider them in connection. 
We may describe the most of these bodies under three 
sub-groups. The type of the first is albumin, or the 
white of egg; of the second, fibrin, or animal muscle; of 
the third, casein, or the curd of milk. 
Common Characters.—The greater number of these 
substances occur in several, at least two, modifications, 
one soluble, the other insoluble in water. 
Tn living or undecayed animals and plants we find the 
albuminoids in the soluble, and, in fact, in the dissolved 
state. They may be obtained in the solid form by evap- 
orating off at a gentle heat the water which is naturally 
associated with them. They are thus mostly obtained as 
transparent, colorless or yellowish solids, destitute of odor 
or taste, which dissolve again in water, but are insoluble 
in alcohol. 
Recently, both in the animal and vegetable, soluble al- 
buminoids have been observed in colorless or red crystals,” 
(or crystalloids,) often of considerable size, but so asso- 
ciated with other bodies as, in general, not to admit of sep- 
aration in the pure state. 
The insoluble albuminoids, some of which also occur 
naturally in plants and animals, are, when purified as much 
as possible, white, flocky, lumpy or fibrous bodies, quite 
odorless and tasteless. 
As further regards the deportment of the albuminoids towards sol- 
vents, some are dissolved in alcohol, none in ether. They are soluble in 
