| McAtep, Shedding of Stomach Lining by Birds. 417 
Wear is manifested also by the lining becoming longitudinally 
grooved, and by strips or broader fragments being gouged out 
(Figs. 3 to 7). In some cases the broken surface of the pad to- 
gether with the shredded portions remaining in position, have a 
distinctly pathologic appearance, and make it hard to realize that 
one observes but a stage in a normal and periodically recurring 
process. 
Apparently after the lining has reached a certain degree of wear, 
general shedding occurs. Then, all the thinner portions of the 
lining usually come off as well as the thick central pads. Rarely 
a bit of the old lining may cling, and if a piece of one of the pads, 
it stands out prominently from the new smooth surface. Such 
pieces gradually wear away from the new lining which bears them. 
Finding fragments of stomach lining among the food is by far the 
most common evidence of the shedding. No fewer than 5 large 
and 20 small pieces of lining have been found in a single stomach. 
It is certain that the normal process in the Anatide is, that the 
worn stomach lining is shed off, ground up, and passed out of the 
body through the intestines. Cases of the regurgitation of the 
lining are what are chiefly recorded in the literature, but in Anatide, 
regurgitation seems practically impossible. 
When the central pads and other parts of the stomach lining are 
freshly shed off, the surface below is not always a new grinding 
surface, but may be the soft mucous coat itself. This is known by 
the fact that objects in the gizzard become imbedded in it, some- 
thing that never happens (except in case of sharp bones, etc.) 
when the horny lining is concerned. Stomachs in this stage are 
empty or nearly so, and it is probable that there is a pause in 
digestive action until a new lining is formed. A useful incidental 
result of shedding the lining is that the bird gets rid of the parasitic 
worms (Nematodes) that frequently lie half beneath, half above 
the lining. 
As to the frequency with which evidences of wear are observed, 
I may say that in a collection of 30 stomachs of ducks from Minot, 
Mass., 4, or 138% showed marked wear; the proportion in another 
lot of 67 from Wenham, Mass., was 24%. I have noted severe 
wear or some stage of the actual shedding process in about 100 
gizzards of the common Mallard, 66 of the Lesser Scaup, 28 of the 
