in the fixed principles of the egg during incubation. 397 
3. That in the earlier stages of incubation, an interchange 
of principles takes place between the yelk and a portion of 
the albumen ; that this interchange is confined on the part of 
the yelk to a little of its oily matter, which is found mixed 
with the above mentioned albumen ; that this portion of 
albumen undergoes some remarkable changes, and is con- 
verted into a substance analogous in its appearance, as well as 
in some of its properties, to the curd of milk ; and lastly, that 
a portion of the watery and saline portion of the albumen is 
found mixed with the yelk, which becomes thus apparently 
increased in size. 
4. That as incubation proceeds, the saline and watery parts 
again quit the yelk, which is thus reduced to its original bulk ; 
that in the last week of the process it undergoes still further 
diminution in weight, and loses the greater portion of its 
phosphorus, which is found in the animal converted into 
phosphoric acid, and in union with lime , constituting its bony 
skeleton ; and lastly, that this lime does not originally exist in 
the recent egg, but is derived from some unknown source 
during the process of incubation. 
These, and other interesting circumstances, arising out of 
the present inquiry, suggest some important hints respecting 
certain operations of the animal economy. They also serve 
to direct the attention of the microscopic inquirer to the in- 
vestigation of points, which it is probably within his power to 
elucidate, but of which, at present, we are ignorant. This 
part of the subject, however, cannot be in abler hands than 
it is at present. To the distinguished physiologists, there- 
fore, who have been recently engaged in the investigation, I 
willingly leave it, and shall conclude with a few remarks only 
