Birds. 9017 
vole is far commoner than is generally supposed.—H. Harpur Crewe; The Rectory, 
Dyayton- Beauchamp, Tring, March 12, 1864. 
On the Gizzard or Stomach of Birds. By W. W. Boutton, Esq. 
SINCE ascertaining that the bittern (Ardea stellaris) digested its 
food by the aid of a true stomach supplied with acrid solvents (Zool. 
8959), instead of mechanically grinding it by means of a gizzard and 
foreign substances, such as stones, grit, &c., I have carefully observed 
the stomach of every bird that has come under my notice. The 
result of my investigations leads me to suppose that there are no less 
than three different forms or types of stomach amongst birds. 
1. I find birds with a true stomach, similar in all essential parts 
and powers to the same organ in animals, and digesting its contents 
by the secretion and action of a natural solvent. Of this class are the 
owl, bittern, &c., birds which prey upon small animals, fish and 
insects. 
2. Birds with a true gizzard or stomach supplied with such an 
arrangement of parts and powers that the food is thereby ground 
mechanically to the consistency required for the purposes of assimila- 
tion, and is not perceptibly acted upon or softened by a natural 
solvent. Of this class are the pochard, domestic fowl and small hard- 
billed birds, &c., birds which live upon vegetable matters, seeds, fruits, 
and a varied or ridxed diet. 
3, Birds with a stomach which appears to be compounded of the 
other two forms; in fact, with a stomach partly supplied with actual 
digestive powers (literally and strictly) and partly with grinding or 
triturating powers. Of this class are the goosander, smew, &c. 
In all birds the esophagus is more or less dilated at its lower end 
where it opens into the gizzard or stomach. This dilatation is called 
the “ ventriculas succenturiatus,” and in the case of the class of birds 
to which I am at present referring, it appears to serve the purposes of a 
digesting stomach more or less perfectly. Itis supplied with a mucous 
membrane and glands, whose fluids possess an undoubted power of 
acting as solvents of the ingesta retained in this portion of the 
alimentary canal. Thus, a fish received into this greatly dilated 
ventriculus succenturiatus would have become so far softened during 
the period of its retention therein, that the scales would slip off on the 
slightest touch, and the whole tissues of the fish would have become 
so far altered in consistency as to be readily crushed into a pulp by 
the representative of a gizzard into which it enters on leaving the 
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