“AS PIGEONS FEED THEIR YOUNG,” 187 
crop when the bird is not sitting, with its appearance 
during incubation, the difference is very remarkable. In 
the first case it is thin and membranous, but by the time 
the young are about to be hatched, the whole, except 
what lies on the trachea or windpipe, becomes thickened, 
and takes on a glandular appearance, having its internal 
surface very irregular. It is likewise evidently more 
vascular than in its former state, that it may convey a 
quantity of blood, sufficient for the secretion of this sub- 
stance, which is to nourish the young brood for some days 
after they are hatched. Whatever may be the consistence 
of this substance when just secreted, it most probably 
soon coagulates into a granulated white curd, for in such a 
form I have always found it in the crop; and if an old 
pigeon is killed just as the young ones are hatching, the 
crop will be found as above described, and in its cavity 
pieces of white curd, mixed with some of the common 
food of the pigeon, such as barley, beans, &c. 
“If we allow either of the parents to feed the young, its 
crop, when examined, will be discovered to contain the 
same curdled substance, which passes thence into the 
stomach, where it is to be digested. The young pigeon is 
fed for some time with this substance only, and about the 
third day some of the common food is found mingled with 
it; and as the pigeon grows older, the proportion of 
common food is increased, so that by the time it is seven, 
eight, or nine days old, the secretion of the curd ceases in 
