398 Mr. Home on the different Structures and Situations 
the right side, they are entirely wanting. The gizzard has a 
portion of its anterior and posterior surfaces opposite each 
other, covered with a horny cuticle. These appearances are 
shewn in the annexed drawing. 
This peculiar formation of the digestive organs of the little 
auk, appears to be fitted for economizing the food ; which may 
be rendered more necessary in a bird, that spends a portion 
of the year in the frozen regions of the North, where supplies 
of nourishment must be very precarious. 
In birds that live principally on vegetable food, the solvent 
glands have a different structure, according to the substances 
the birds are intended to feed upon, and vary a good deal in 
situation, according to the habits of life. The following are 
the most remarkable instances of such difference, both with 
respect to structure and situation. 
In the pigeon (Columba domestica), their situation is 
the same as in the genus falco, but their size is small, the 
external orifices large, and the coats thin, so that they 
resemble the glands in the English heron, but having larger 
cavities. 
In the swan, the (Anas Cygnus), the solvent glands appear 
to be cylinders, as in the genus falco, but are not straight, 
bending upon one another in a direction obliquely upwards ; 
their internal surface is not villous as in the genus falco, but 
rather broken and irregular. 
In the goose (Anas Anser), the solvent glands have the 
same situation as in the swari, and resemble them in their exter- 
nal appearance, but when laid open the sides are found to be 
cellular. 
In the common fowl (Phasianus Gallus), these glands are 
