gg,6 Mr. Home on the different Structures and Situations 
fish bones held together by mucus, was found in the cavity of 
the gizzard. 
In the cormorant, (Pelecanus Carbo), the situation of 
the solvent glands is the same as in the Soland goose, but 
they only form two circular spots, one anterior, the other 
posterior.* 
In all these birds, the inner membrane of the gizzard is 
soft and smooth, but that portion which covers the solvent 
glands, has a more spongy or villous appearance; and this 
part is found to secrete a mucus which the other parts do not. 
This fact appears to be ascertained by the following circum- 
stances: on examining the gizzard of a cormorant that died 
in consequence of an inflammation in the oesophagus, which 
had been communicated to the internal membrane of the 
gizzard, a viscid mucus was found upon the surface covering 
the solvent glands, and this was not met with in any other part, 
so that the mucus had been evidently secreted there, and was 
afterwards coagulated by the liquor of the solvent glands 
poured upon it, coagulation being the first process which takes 
place in the act of digestion. This explains the circumstance 
of ascarides being frequently found enveloped in mucus in 
this part of the cormorant’s gizzard, the mucus on which 
they feed being secreted in consequence of the irritation they 
produce on the membrane. In the same manner the flukes in 
the biliary ducts of the sheep, increase the secretion of the 
bile by irritating these canals, and then feed on it. 
It is generally believed that mucus is secreted by surfaces as 
well as by glandular structure, but I know of no evidence that 
* An engraving of this gizzard is given in the Phil. Trans, for the year 1807, 
pi. x. p. 178. 
