bint ed McAtes, Shedding of Stomach Lining by Birds. 415 
THE SHEDDING OF THE STOMACH LINING BY BIRDS, 
PARTICULARLY AS EXEMPLIFIED BY 
THE ANATIDA. 
BY W. L. MCATEE. 
Plates XVI-XVII. 
At the beginning of this discussion, it is well to make sure that 
all understand the true nature of the stomach lining of birds. 
Besides the innermost lining with which we are now especially 
concerned, the stomach wall in birds consists of three layers: the 
external serous or connective tissue coat, the middle muscular 
layer, which varies greatly in development, in the different groups 
and the inner glandular or mucous coat. In section, as viewed 
through the microscope, the mucous coat is seen to consist chiefly 
of innumerable long slender villi. It is among these that the 
material is secreted that forms the innermost or fourth coat of the 
stomach. This lining is of a horny but somewhat flexible con- 
sistency. It strips rather easily from the mucous coat, and when 
freshly pulled off its inner surface has a furry appearance. When 
examined under the microscope the filaments giving it this appear- 
ance are seen to continue into the mucous coat. This interdigita- 
tion must aid greatly in holding the corneous lining in place, during 
the digestive process, which is a strenuous one, particularly in birds 
with highly developed grinding gizzards, as the Anatide. 
To emphasize the intensity of the grinding process in which the 
stomach lining takes part, it may be well to give an idea of the 
power exerted by the gizzards of birds. De Reaumur found that 
small tin cylinders fed to turkeys were crushed by the gizzard in 
a short time; and pellets of shot in gizzards often are greatly 
flattened. Wild ducks habitually feed on such things as acorns 
and hickory nuts and have no difficulty in grinding them up. In 
fact, according to the writer’s experience, bitter pecans which 
have a thick hard shell are cracked as they enter the gizzard, and 
before they can possibly have been exposed to the maximum 
pressure. Many species of ducks feed upon thick-shelled mollusks, 
