222 GENERAL ORNITHOLOGY. 
which gets hold of the ovum to drag it down to the common lot of mortals from its high ovarian 
birth. The infundibulum receives from the mesentery a delicate tunic of unstriped muscular 
fibres, which are so disposed as to dilate that orifice for the reception of the ovum ; and during 
the venereal orgasm the mouth of the tube is supposed to seize upon the ripest egg. The 
actual anatomy of the arrangement, and the whole operation, is strangely suggestive of one of 
the oldest myths respecting the serpent which bore the egg of the world in its jaws. The 
mucous lining of the oviduct consists of a layer of ciliated epithelium ; the membrane has a 
different character in successive portions of its extent. Above, when the tube is not distended 
with its burthen, the lining is thrown into lengthwise folds, which lower down become spirally 
disposed, and then longitudinal again before they cease. This rugous portion of the tube is 
beset with mucous follicles, which secrete "the white." The oviduct, after contracting at a 
point called the isthmus, enlarges to a calibre sufficient to accommodate the egg in its shell ; 
for this is the shell-forming part, homologous with the mammalian uterus (a sinister semi -uterus 
at least), lined with large villi, and beset with the follicles whose secretions calcify the egg-shell, 
and decorate it with pigment. The rest of the tube is vaginal, being merely the passage-way 
by which the perfected ovum is discharged into the cloaca, to be expelled per anum. The 
muscular walls of the oviduct consist of both circular and longitudinal unstriped fibres, like 
those of intestine, — the latter especially in upper portions and at the infundibulum, the former 
more conspicuously below, where they form a sort of os tincce at the bottom of the calcific 
portion, and a kind of sphincter vagince at the end of the tube. A recognizable clitoris is 
developed in many birds. 
The deposition of the M^hite and of the shell 
remains to be noticed. The first deposit upon 
the yelk-ball consists of a layer of dense and 
somewhat tenacious albumen, called the chala- 
ziferous membrane (Gr. x'^^'^C^j chalaza, a tu- 
bercle, and Lat. /ero, I bear). As the egg is 
urged along by the peristaltic action of the 
tube, it acquires a rotation about the axis of the 
tube; the successive layers of soft albumen it 
receives are deposited somewhat spirally ; and 
the chalaziferous membrane is drawn out into 
threads at opposite poles of the egg. These 
threads, M'^hich become twisted in opposite direc- 
tions during the rotation of the egg, are called 
chalazce ; they are the '^strings," rather un- 
pleasantly evident in a soft boiled egg, but serve 
the important office of mooring and steadying the 
yelk in the sea of white by adhesions eventually 
contracted with the membrane which immedi- 
ately lines the shell. They are also intrusted 
with the duty of ballasting, or keeping the yelk right side up. For there is a ''right side" 
to the yelk-ball, being that on which floats the cicatricle, or "tread." This side is also the 
lightest, the white yelk being less dense than the yellow ; and the chalazse are attached a little 
below the central axis. The result is, that if a fresh egg be slowly rotated on its long axis, 
the tread will rise by turning of the yelk-ball in the opposite direction, till, held by the twisting 
of the chalazse, it can go no farther ; when, the rotation being continued, the tread is carried 
under and up again on the other side, resuming its superior position as before. After all the 
spiral layers of soft white are laid on, a final covering of dense albumen is deposited at the 
isthmic part of the oviduct. This forms a tough tunic called the membrana putaminis (Lat. 
Fig. 110. —Hen's egg, nat. size, in section; from 
Owen, after A. Tliompson. A, cicatricle or "tread," 
witli its nucleus, of white germ-yelk, floating on surface 
of pale thin nutritive yelk, leading to central yelk- 
cavity, X ; a, the yellow yelk-ball, deposited in the suc- 
cessive layers, forming a set of halones, and enveloped 
in the chalaziferous membrane which is spun out at 
opposite poles into the twisted strings, chalazae, c, c; 
h, ¥, successive investments of softer white albumen ; 
d, membrana putaminis, the "soft shell" or egg-pod, 
between layers of which at the great end of the egg is 
the air space,/; e, the shell. 
