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94 THE PROTEIN SUBSTANCES.
I. Simple Proteins.
A. True Albuminous Bodies.
The albuminous bodies are never-failing constituents of the animal
and vegetable organisms. They are especially found in the animal
body, where they form the solid constituents of the muscles and of the
blood-serum, and they are so generally distributed that there are only
a few animal secretions and excretions, such as the tears, the perspira-
tion, and perhaps the urine, in which they are entirely absent or occur
only in traces.
All albuminous bodies contain carbon, hydrogen, nitrogen, oxygen
and sulphur;1
a few contain also phosphorus. Iron is generally found
in traces in their ash. The elementary composition of the different
albuminous bodies varies a little, but the variations are within relatively
close limits. For the better-studied animal albuminous bodies the
following composition of the ash-free substance has been found:
C 50.5 —54.6 percent
H 6.5 — 7.3 "
N 15.0 —17.6 "
S 0.5 — 2,2 "
P 0.42— 0.85 "
21.50—23.50 "
The animal proteids are odorless, tasteless, and ordinarily amorphous.
The crystalloid spherules (Dotterplattchen) occurring in the eggs of certain
fishes and amphibians, do not consist of pure proteids, but of albuminous
bodies containing large amounts of lecithin, which seem to be combined
with mineral substances. Crystalline proteids 2
have been prepared
from the seeds of various plants, and crystallized animal proteids (see
seralbumin and ovalbumin, Chapters V and XII) can be readily pre-
pared. In the dry condition the proteids appear as white powders,
or when in thin layers as yellowish, hard, transparent plates. A few
are soluble in water, others only soluble in salt or faintly alkaline or acid
solutions, while others are insoluble in these solvents. Solutions of
proteids are optically active and turn the plane of polarized light to the
left. All proteids when burned leave an ash, and it is therefore ques-
1
See foot-note 1, p. 80.
2
See Maschke, Journ. f. prakt. Chem., 74; Drechsel, ibid. (N. F.), 19; Griibler,
ibid. (N. F.), 23; Ritthausen, ibid. (N. F.), 25; Schmiedeberg, Zeitschr. f. physiol.
Chem., 1; Weyl., 1; ibid., 1.
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