INTRODUCTORY. 
As the yolk becomes fully matured, the en¬ 
closing membrane or ovisac becomes gradually 
thinner, especially round its greatest diameter 
or equator, which then exhibits a pale zone or 
belt called the stigma. Finally, whether or not 
fecundation takes place, the sac ruptures at 
the stigma, and the liberated yolk and germ, 
surrounded by a very thin and delicate mem¬ 
brane, is received by the funnel-shaped opening 
of the oi'idact or egg-passage, whose office it. is 
to convey it to the outer world, and on its way 
to clothe it with other structures needful for its 
development and preservation. This organ, 
with its various convolutions a little modified 
for convenience of 
representation, i s 
shown in the illus¬ 
tration, and in an 
ordina r v hen is 
nearly two feet in 
length. It will 
easily be seen how 
two yolks may be¬ 
come detached and 
enter the oviduct 
at nearly the same 
time; in which case 
they are likely to 
be developed in the 
same white and 
shell, causing the 
“ doub le-yolked 
egg” so well-known 
to every p o u 11 r y 
keeper. 
Thus received 
into the oviduct, 
the yolk becomes 
enveloped in a 
glairy fluid called the white, or by chem¬ 
ists albumen. This is secreted by the 
mucous membrane of the oviduct, and added 
layer by layer as the egg passes on. The uses of 
the white or albumen are manifold. It is emi¬ 
nently nutritious, forming indeed the chief 
nourishment of the chick during its growth in 
the shell; as it becomes absorbed by the little 
animal, and forming as it does by far the greater 
part of the egg when laid, it gives the fast- 
growing little body the needed increase of room; 
it is a very bad conductor of heat, and hence 
guards the hatching egg against the fatal chills 
which would otherwise occur when the hen left 
the nest; and finally it preserves the delicate 
yolk and vital germ from concussion or other 
violent injury. 
At a still further point of the oviduct the egg 
becomes invested with the skin or parchment¬ 
like covering which is found inside the shell. In 
realitv this skin consists of two lavers, which 
can easily be separated, and at the large end of 
the egg they do separate entirely, forming the 
air-chamber. At first this chamber is small, 
but as the egg gets stale, it becomes larger and 
larger, so that even in eggs stored, it fills at 
length, a large portion of the space within the 
shell, the egg itself drying up in proportion. In 
eggs on the point of hatching it usually occu¬ 
pies about one-fifth of the space. It has been 
proved by experiments that the perforation of 
this air chamber, even by a needle point, is an 
effectual prevention of successful hatching. 
In the last portion of the oviduct, the egg be¬ 
comes coated with that calcareous deposit which 
forms the shell, after which it passes into the 
cloaca and is ready for expulsion. In some 
breeds, coloring matter is added over the solid 
ingredient, producing the deep-colored eggs of 
the Cochin, and in other birds the splashed and 
spotted patterns so well-known. In fowls which 
lav colored eggs similar splashes often occur, and 
we have had Brahma hens which laid eggs with 
a white ground, covered thickly over by choco¬ 
late-colored spots. We have had others, again, 
lay eggs covered apparently with a coat of 
white-wash, which on being rubbed off with a 
rough cloth, revealed the usual buff-brown tint 
beneath. All these things obviously depend on 
some peculiar condition of the secreting organs, 
as does the shape of the egg of each bird when 
finally laid. 
Occasional departures from the ordinary 
type of egg will now be understood. If the lat¬ 
ter portion of the oviduct be in an unhealthy 
condition, or if the yolks be matured by the ovary, 
faster than shells can be formed by that organ, 
“soft” or unshelled eggs will bo produced. If, 
on the contrary, the oviduct and its glands be 
active, while the supply of yolks is temporarily 
exhausted, the diminutive eggs, which consist of 
only white and shell, and which not infrequent¬ 
ly terminate the laying of a long batch, may be 
expected to occur. Disease extending to the 
middle portion of the passage may result in eggs 
without even the membraneous skin, and if the 
entire canal be in an unhealthy condition, yolks 
alone may probably be dropped without any 
addition whatever, even of whites. This last 
9 
