360 
BIRDS. 
formation; the shell has the last, and hardens from 
day to day. The shell enables the mother to dis- 
charge the egg without crushing it ; while its soft 
contents preserve the young from all accidents, till 
it is completely formed, and in a condition to make 
its appearance. We may even say, that the egg 
performs to young birds the office of the breast 
milk, with which the offspring of other animals are 
nourished, because the little chick who lies in the 
egg is first sustained by the white, and afterwards 
with the yolk when the animal has gained a little 
strength and its parts begin to be fixed. Under the 
membrane which surrounds the yolk is found a lit- 
tle cicatrice, or white spot, which is only the seed, 
where the chick resides in miniature. It has all its 
organs at that time, but they are wrapped up and 
comprehended in a point. If the smallest portion 
of that vital spirit, which is destined to animate the 
mass, be then infused into it, by a process of which 
we can have no idea ; the chick receives life at the 
same instant, and its whole substance is then in 
motion. We have no adequate conception, indeed, 
of a vital spirit ; but this expression points out a 
reality, which is sufficient for our purpose. 
When the vital principle has not been infused into 
this speck, which comprehends not only the first 
sketch, but every part of the chick, the dam then 
sometimes lays that egg; but it will contain nothing 
more than an unprolific nourishment, and will never 
be a living animal. On the contrary, should this 
enlivening spirit be transmitted, in the minutest de- 
