THE EGG 23 
nature of the shell, as there is not room for two eggs side by side 
in the lower part of the body-cavity. 
The ovary hes at the anterior end of the kidney attached 
by a fold of the peritoneum (mesovarium) to the dorsal wall of 
the body-cavity. In a laying hen ova of all sizes are found from 
microscopic up to the fully formed ovum ready to escape from 
the follicle. Such an ovary is shown in Figure 4; the gradation 
in size of the ova will be noticed up to the one fully formed and 
ready to burst from its capsule. At 5 in this figure is shown a 
ruptured follicle, and the ovum which has escaped from this 
follicle is shown in the oviduct at 8. It will be seen that the part 
of the definitive hen’s egg produced in the ovary is the so-called 
yolk. The blood-supply of the very vascular ovary is derived 
from the dorsal aorta, and the veins open into the vena cava 
inferior. 
The oviduct is a large coiled tube (Fig. 4) which begins in a 
wide mouth with fringed borders, the ostiwn tube abdominale 
(funnel or infundibulum) opening into the body-cavity near the 
ovary. It is attached by a special mesentery to the dorsal wall 
of the body-cavity, and opens into the cloaca. The following 
divisions are usually distinguished: (1) the oviduct s. s., (2) the 
uterus, (3) the vagina (Fig. 4). The oviduct includes the entire 
tube from the funnel to the dilated uterus. The vagina is the 
short terminal portion opening into the cloaca (Figs. 4 and 5). 
In the oviduct proper we distinguish the funnel, the main glandu- 
lar part, and the isthmus. 
The formation of an egg takes place as follows: the yolk, or 
ovum proper, escapes by rupture of the follicle along a preformed 
band, the stigma (Fig. 4-4), into the infundibulum which swallows 
it, so to speak, and it is passed down by peristaltic contractions 
ova are shown in the oviduct at different levels; normally but one ovum 
is found in the oviduct at a time. 
1, Ovary; region of young follicles. 2 and 38, Successively larger follicles. 
4, Stigmata, or non-vascular areas, along which the rupture of the follicle 
takes place. 5, Empty follicle. 6, Cephalic lip of ostium. 7, Funnel of 
oviduct (ostium tubs abdominale). 8, Ovum in the upper part of the ovi- 
duct. 9, Region of the oviduct in which the albumen is secreted. 10, Albu- 
men surrounding an ovum. 11, Ovum. 12, Germinal dise. 13, Region 
of the oviduet in which the superficial layers of albumen and the shell-mem- 
brane are formed. 14, Lower part of the oviduct (‘‘uterus,” shell-gland). — 15, 
Rectum. 16, Reflected wall of the abdomen. 17, Anus, or external opening 
of cloaca. 
