THE BEAUTIFUL LADDER. 
235 
Oftentimes the food is swallowed in size nearly 
as large as the head of the bird, as in the case 
of the wild pigeon. From the crop of one of 
these birds there were taken three of the larg¬ 
est acorns grown in the West, either one of 
which was nearly the size of the pigeon’s head. 
When swallowed the shells were unbroken, be¬ 
ing dry and very hard. To one unacquainted 
with the physiology of birds, it would seem 
impossible for the greedy creature to dispose 
of such cumbersome materials; and hence one 
might infer that death must ensue from gorg¬ 
ing such intractable substances. But open the 
distended craw, and see if it will reveal the 
marks of inadequate skill. No; there is an 
arrangement just adapted to the contingencies 
of the case. The craw is made up of two ex¬ 
ceedingly muscular halves or valves, lined with 
deeply-corrugated vellum-like skin, capable of 
indefinite and strong contraction and expansion. 
Now mark the marvellous provision for meeting 
the special needs of the bird. With the food a 
quantity of small gravel-stones are swallowed, 
and by the muscular contraction of the crop the 
contents are ground into a pulpy mass easily 
digested and assimilated. 
