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638 ORGANS OF GENERATION.
tion; on the fourth day the carbon-dioxide production gradually increases,
and after the ninth day it augments in the same proportion as the weight
of the foetus. Calculated upon 1 kilogram weight for one hour it is,,
from the ninth day on, about the same as in the full-grown hen. Hassel-
balch l
has also shown that the fertilized hen’s egg not only gives off
nitrogen the first five or six hours of incubation, but also some oxygen,
and that we are here dealing with an oxygen production which runs
parallel with the cell-division. It is not known whether this oxygen
formation connected with the life of the cell is a fermentative or a so-
called vital process.
While the quantity of dry substance in the egg during this period
always decreases, the quantity of mineral bodies, protein, and fat always
increases in the embryo. The increase in the amount of fat in the
embryo depends, in great part upon a taking up of the nutritive yolk
in the abdominal cavity. Plimmer and Scott 2
have observed in the incu-
bation of the hen’s egg, that a rapid diminution of phosphorized substances
soluble in ether takes place, while at the same time an increase in the
inorganic phosphorus is found in the chick.
The weight of the shell and the quantity of lime-salts contained therein
do not remain unchanged, according, to the recent investigations of
Tangl.3
The egg-shell (lime shell, and shell-membrane) of a hen’s egg
weighing 60 grams loses (calculated on the dry) during incubation about
0.4 gram, of which 0.15 gram is calcium and 0.2 gram is organic substance.
A very complete and careful chemical investigation on the develop-
ment of the embryo of the hen has been made by Liebermann.4
From
his researches we may quote the following: In the earlier stages of the
development, tissues very rich in water are formed, but upon the con-
tinuation of the development the quantity of water decreases. The
absolute quantity of the bodies soluble in water increases with the develop-
ment, while their relative quantity, as compared with the other solids,
continually decreases. The quantity of the bodies soluble in alcohol
quickly increases. A specially important increase is noticed in the fat,
whose quantity is not very great even on the fourteenth day, but after
that it becomes considerable. The quantity of protein bodies and albu-
minoids soluble in water grows continually and regularly in such a way
that their absolute quantity increases, while their relative quantity
remains nearly unchanged. Liebermann found no gelatin in the
1
Bohr and Hasselbaleh, Maly’s Jahresber., 2i); Hasselbalch, Skand. Arch. f.
Physiol., 13.
2
Journ. of Physiol., .’{S.
a
Tangl with Hammerschlag, Pfliiger’s Arch.. 121.
* 1. c.
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