Z 377 3 
XXVIII. Some experiments on the changes which take place in 
the fixed principles of the egg during incubation. By William 
Prout, M. D. F. R. S. 
Read June 20, 1822. 
In the year 1816, I was induced to commence a series of 
experiments on the egg during incubation, with the view of 
ascertaining the nature of the changes which take place du- 
ring that process. My inquiry was chiefly limited to the 
fixed principles, namely, the earthy and saline matters ; but 
my attention was more particularly directed to the source 
whence the earthy matter, constituting the skeleton of the 
chick, was derived. 
With these views, the egg was analyzed in its recent and 
unaltered state, and at the end of the first, second, and third 
weeks of incubation. My experiments were chiefly confined 
to the eggs of the domestic fowl, but have been likewise par- 
tially extended to those of the duck and turkey. The in- 
vestigation has been renewed, and the experiments repeated 
at various intervals since the period above mentioned ; but 
the difficulty of the subject, and various accidents, have pre- 
vented me from completing them till the present time ; and 
the results, which, after all, are much less perfect than I 
could wish, I have now the honour of submitting to the 
Society. 
3c 
MDCCCXXII. 
