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636 ORGANS OF GENERATION.
284.5 grams potash, 235.6-329.3 soda, 17.4-29.0 lime, 17-31.7 magnesia,
4.4-5.5 iron oxide, 238.4-285.6 chlorine, 31.6-48.3 phosphoric acid (P2 5),
13.2-26.3 sulphuric acid, 2.8-20.4 silicic acid, and 96.7-116.0 grams carbon
dioxide. Traces of fluorine have also been found (Nickles 1
). The
white of egg contains, as compared with the yolk, a greater amount of
chlorine and alkalies and a smaller amount of lime, phosphoric acid, and
iron.
The Shell-membrane and the Egg-shell. The shell-membrane con-
sists, as above stated (page 112), of a keratin substance. The shell con-
tains very little organic substance, 36-65 p. m. The principal mass, more
than 900 p. m., consists of calcium carbonate; besides this there are very
small amounts of magnesium carbonate and earthy phosphates.
The diverse coloring of birds’ eggs is due to several different coloring-matters.
Among these we find a red or reddish-brown pigment called " oorodein " by
Sorby, 2
which is perhaps identical with hsematoporphyrin. The green or blue
coloring-matter, Sorby’s oocyan, seems, according to Liebermann 3
and Kruken-
berg, 4
to be partly biliverdin and partly a blue derivative of the bile-pigments.
The eggs of birds have a space at their blunt end filled with gas; this
gas contains on an average 18.0-19.9 per cent oxygen (Hufner 5
).
The weight of a hen’s egg varies between 40-60 grams and may some-
times reach 70 grams. The shell and shell-membrane together, when
carefully cleaned, but still in the moist state, weigh 5-8 grams. The
yolk weighs 12-18 and the white 23-34 grams, or about double. The
entire egg contains 2.8-7.5, or average 4.6, milligrams of iron oxide, and
the quantity of iron can be increased by food rich in iron (Hartung 6
)
.
The white of the egg of cartilaginous and bony fishes contains only traces of
true albumin, but consists, at least in many fishes, of mucin substance; and the
cover of the frog’s egg also consists, according to Giacosa, of mucin. The eggs
of the river-perch contain, Hammarsten 7
claims, mucin in the envelope in the
unripe state and only mucinogen in the ripe state. The crystalline formations
(yolk-spherules, or dotterpldttchen) which have been observed in the egg of the
tortoise, frog, ray, shark, and other fishes, and which are described by Valen-
ciennes and Fremy under the names emydin, ichthin, ichthidin, and ichthulin,
seem, as above stated in connection with ichthulin, to consist mainly of phos-
phoglycoproteins. The klupeovin obtained by Hugounenq 8
from the herrings’
eggs and from which he obtained the three so-called hexone bases and abundant
1 Compt. Rend., 43.
2 Cited from Krukenberg, Verb. d. phy.s.-cbem. Gessellsch. in Wurzburg, 17.
8
Ber. d. deutsch. chem. Gesellsch., 11.
•lie.
6
Arch. f. (Anat. u). Physiol., 1892.
»Zeitechr. f. Biol., 43.
7
Giacos;i, Zeitschr. f. physiol. Chem., 7; Hammarsten, Skand. Arch. f. Physiol., 17.
8 Valenciennes and Fremy. eited from Hoppe-Seyler, Physiol. Chem., p. 77;
Hugounenq, Bull. soc. chim. (3), 33, and Compt. Rend., 143.
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