of Grazing Birds. 187 
In the goose, the gizzard differs very much in its external 
form, from that of the turkey; being oval in its transverse 
direction, and having the lateral edges very thin ; this arises 
from the fasciculi of fibres of both muscles being more 
numerous than in the turkey. The disproportion between 
the left muscle and the right, is still greater than in the tur- 
key, and when the cavity is opened it is flat, divided into 
two equal portions ; that on the right side convex above, 
forming a projection into the cavity, and concave below, 
forming a hollow. On the left side there is a corresponding 
surface, only that the concavity is above, answering to the 
convex part opposite ; and a convexity below, fitted to the 
opposing concavity. 
The horny covering of these surfaces is very strong, much 
more so than in the turkey, and when the structure is 
examined, the direction of its fibres is oblique ; on the right 
side from above downwards, and on the left side from below 
upwards. 
In the swan, the gizzard is altogether larger than in the 
goose, and more flattened at the external edge, so that the 
muscular fibres are shorter ; on its internal cavity the appear- 
ances are nearly the same, but there is a less strongly marked 
ridge and concavity, and the surface of the oval portion, in 
which these are met with, is smaller in size. The substance 
of that part of the gizzard appears to be less dense, but the 
cuticular covering is thicker, and its fibrous texture more con<- 
spicuous. The direction of the fibres is exactly the same as 
in the goose. 
From this construction of cavity it is evident, that these two 
corresponding surfaces are intended to move on one another* 
