202 POULTRY BREEDING 
the yolk is admitted to'the stomach. When the chick 
first emerges from the shell the yolk lies in the stomach 
as feed for the chick until it shall have gained strength 
to eat for itself, and the process of digestion and assimi- 
lation begins at once. The yolk supplies all the feed 
needed for the first 48 hours, and no chick should be fed 
until this period has elapsed, as such feeding may so 
disarrange the digestive system that very serious results 
may follow. 
The first change after the process of incubation has be- 
gun is the formation of a tiny blood speck as the heart 
of the embryo begins to perform its functions. A few 
hours later this minute speck of blood has divided into 
a V-shaped form and the circulation has begun. From 
this rudimentary heart veins begin to branch out and 
through these the albumen in the white of the egg is 
changed to blood and this in turn contributes to the 
growth of the body and vital organs of the chick through 
the wonderful alchemy of nature. At the end of two days 
the pulsation of the blood is plainly visible. One branch 
of this rudimentary circulatory system is the left ven- 
tricle of the heart and the other is the great artery. At 
the 50th hour one auricle of the heart appears and the 
beating of the heart may be observed. Gradually the 
blood vessels extend themselves through the umbilical 
cord and a network of veins is formed which extends 
along the inner side of the shell through which oxygen 
must come for the purification of the blood and to make 
the life processes possible. At this time if a thin-shelled 
egg be observed through an egg tester the appearance of 
the embryo will be that of a many-legged insect, the 
heart being the body and the radiating blood veins the 
legs. 
