GENERAL DISEASES ' 169 
multiplication is already taking place in this disc, from which the 
embryo develops. The yolk is composed of a central light colored 
portion (Fig. 18) and an outer mass colored a deeper yellow. The 
latter is formed of concentric layers showing different stages of yolk 
deposit (Fig. 18). The germinal dise and yolk are surrounded by 
a thin strong vitelline membrane (Fig. 18). The ovarian ovum on 
entering the oviduct is passed along by peristaltic movement in a 
rotary course to its completion in the uterus or shell secreting por- 
tion. In the anterior portion of the oviduct the membrane chal- 
azifera is applied over the vitelline membrane. It consists of a 
dense layer of albumin and gives rise to the two chalaze which ex- 
tend from each pole of the ovum. These strands become twisted in 
opposite direction during the further passage of the ovum through 
the oviduct. Over the chalaziferous membrane are several albumi- 
nous layers secreted by the glands of the oviduct. When the ovum 
enters the isthmus or narrow portion two egg membranes are secreted. 
These become separated at the large end of the egg as air is absorbed. 
The shell is acquired in the uterus. 
FOREIGN BODIES IN EGGS 
Eggs may contain a variety of foreign bodies such as pebbles, frag- 
ments of plants, feathers, roundworms, ete. Such bodies after gain- 
ing access to the cloaca penetrate the oviduct far enough to encounter 
an egg and thus be included within the shell. 
Otherwise normal eggs have been found to contain such parasites 
as the fluke Prosthogonimus ovatus and the roundworm Ascaridia 
perspicllum. The latter worm may be present surrounded by al- 
bumin in an abnormal egg lacking a yolk. It is apparent that under 
such circumstances the presence of the worm has stimulated the secre- 
tion of the albumin. Tapeworms and segments of the same have been 
found in eggs. The parasites found in eggs evidently have migrated 
into the oviduct for a sufficient distance to meet a developing egg and 
to become enclosed in shell. Parasites of microscopic size such as 
coccidia, amebee, aspergillus fungi and bacteria have been demon- 
strated in eggs. 
BLOOD SPOTS IN EGGS. (LIVER SPOTS) 
It frequently happens that streaks of blood, or clots of varying size 
are found in eggs. This abnormality is especially noticed during the 
heavy laying period. At such time the ovary is plentifully supplied 
