DEYELOPEMENT. 
69 
rapidity; the germ-spot extends itself more and more 
over the yolk, at the same time becoming more susceptible 
of developement. 
The third day is fraught with no less importance for 
the young life. The cardiac tube begins slowly to expand 
and contract; it throws off the blood already collected in 
it, and takes it up again. At the further extremity of the 
four hillocks, lying across and in front of them, a tube is 
formed, which pushes itself outwards from the inside, 
and subsequently forms the mouth. The blood-vessels 
increase in number almost visibly. On one of the 
principal veins of the heart new forms also appear, and 
their lobes, with numerous ramifications : the deposits for 
the liver and the portal system of veins, which are so 
important. Small inturgescences arise above the heart 
with still smaller knobs; these form the commencements of 
lungs and windpipe; singular folds among these form the 
future intestinal canal. The principal advance in the third 
day’s growth, however, is the division of the skin of the 
germ on either side of the place where it is alive. Their 
lower portions now become two flakes, which grow together, 
so as to enclose the breast and stomach; the upper parts, 
on the contrary, form the first mantle, in which the little 
bird is enveloped until almost the very hour of its 
egress from the shell, or the first cradle, in which the 
little being, already become somewhat substantial, remains 
sheltered, until fully prepared for its entrance into the 
exterior world. At the time of its adjustment in this 
cradle it moves for the first time, turning itself, with the 
side of its head to the right. Through this the heart 
takes its proper position. 
In the course of the two next days the following may 
be observed, even by the less initiated. The division 
