of Grazing Birds. 189 
and mixed with the secretions poured out by the glandular 
surfaces surrounding it, in this respect corresponding to the 
first and second stomach of ruminating animals, in which the 
grass is prepared for mastication. 
These facts, as they account for the goose and swan living 
upon a species of food not fitted for birds in general, proves 
that in this class of animals, a peculiar conformation of the 
digestive organs is required, as well as in quadrupeds, when 
they are intended by nature to live intirely upon grass. 
This fact being ascertained, is not without its importance in 
elucidating this branch of physiological inquiry. 
EXPLANATION OF THE PLATE. 
Fig. 1. The gizzard of a turkey laid open on its anterior 
part, to shew the form of the internal cavity, which is oval, 
and the grinding surfaces uniformly concave. 
Fig. 2. The gizzard of a swan exposed in the same way ; 
the grinding surfaces have an oval form, but in an opposite 
direction to those of the turkey, and each of them is made up 
of a ridge and a hollow in the direction of the oval, which are 
adapted to those of the opposite side, the ridge of the one 
fitting the hollow of the other. 
MDCCCX. 
Cc 
