170 DISEASES OF DOMESTICATED BIRDS 
with blood to promote the rapid formation of ova. As an ovarian 
follicle ruptures to release an ovum some blood may escape from a 
congested blood vessel of the follicle. The blood passes into the 
oviduct aleng with the ovum where it becomes surrounded by al- 
bumin and is incorporated in the egg. The size of the spot or clot 
depends upon the amount of blood which has escaped. These clots 
are often taken for pieces cf flesh and are commonly referred to as 
liver or meat spots. The wholesomeness of such an egg is not im- 
paired. There is no practicable means known for preventing the 
occurrence of blood spots in eggs. However by candling the entire 
product of a flock, it is possible to prevent such eggs from going on 
the market. 
DISCOLORED YOLKS 
Newly laid eggs in some instances exhibit a darkened appearance 
of the yolk which is not due to developmental changes in the ovum or 
to decomposition as a result of bacterial action. The entire yolk 
may appear dark in color or the discoloration may be confined to 
spots or streaks on the surface or in the depths of the yolk material. 
In testing for freshness by candling or on opening the egg, such a 
discoloration may be mistaken for an evidence of addling. The con- 
dition results apparently from the action of sulphur, normally pres- 
ent in the yolk, on small globules of cottonseed oil which are absorbed 
into the yolk. This occurs when the fowls are being fed cottonseed 
meal or material containing cottonseed oil. This oil may be present 
in table scraps since it is often an ingredient of butter, ‘oleomar- 
garin or cooking oils. Cattle or hog fats or their products may 
contain cotton seed oil where the animals have been fed cotton 
seed meal shortly before slaughter. 
Yolk is composed of albumin 17.50 per cent, oil and salts 28.75 
per cent, and water 53.75 per cent. The yolk granules are ar- 
ranged in thin concentric layers as they are received through the 
surrounding vitelline membrane from the blood vessels in the ovarian 
capsule or follicle. This arrangement would explain the disposi- 
tion of the discoloration, depending on whether the fowl was re- 
ceiving cottonseed oil constantly or only at intervals. The color 
reaction between sulphur and cottonseed oil is utilized in the 
Halphen test for the presence of the latter as an adulterant in 
certain food products. In a positive test a pink color is produced 
but this is changed in the yolk to a brownish or dark yellowish color. 
It is not improbable that discolored yolks may result also from the 
