THE STOMACH. 
61 
the finger, the muscles will feel to the touch as hard as 
stones ; when they relax, the grain, upon which they 
were then working, passes on, and a further supply, 
as in the case of the mill, passes under these natural 
rollers. These alternate actions succeed each other 
slowly but regularly; and on placing the bird close 
to the ear, as the food and stones roll under the 
pressure of the muscles of the gizzard, a sound not 
unlike the noise of the tide rolling upon a shingly 
shore, may be distinctly heard at intervals, as if the 
waves were ebbing and flowing ; and during all this 
process, the gastric juice slowly flows in from the 
lower part of the gullet or second stomach, and 
mingles intimately with the digesting food. 
We have stated that the fowl best calculated for 
this examination should be a full-grown young one ; 
but although, in this almost immature state, the 
gizzard is fully developed, if we were to dissect a 
chick, we should find not a vestige of a gizzard, but 
merely a thin pellicle or skin. And it is for this 
reason, that whereas the young fowl is nevertheless 
old enough to live entirely on grain, and therefore 
requires the assistance of a gizzard, the little chick, 
on emerging from its shell, for a short time lives on 
soft food, and requires no such aid. As it advances 
in age, however, the pellicle gradually thickens, till 
at last, by pressure and rubbing, it becomes a hard 
and grinding membrane. 
From the different construction and digestive 
powers of the stomachs of birds, it must be evident 
that some are able to continue a much longer time 
without food than others. An Eagle has been known 
to fast for three weeks ; those who had the charge 
