THE STOMACH. 
51 
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 alter- 
nate actions succeed each other slowly hut 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 exa- 
mination 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 of it having forgotten to provide its usual 
supply of food. It soon, however, recovered its strength, 
and did not appear to suffer from its extraordinary abstinence. 
How long other birds can sustain hunger, we can have few 
opportunities of learning, but probably it will be found that 
such as are most likely, from their habits and particular sort 
of food, to be more exposed to a precarious and doubtful 
supply, are, generally speaking, best provided against the 
chance of suffering. But this is not always the case, for 
E 2 
