Jan., 1920 A PECULIAR FEEDING HABIT OF GREBES 19 
The stomachs of our grebes are large and capacious, with strong muscular 
walls, though the thickened lenticular muscle masses characteristic of the giz 
zards of gallinaceous birds, ducks and others of similar food habit are absent. The 
upper division of the stomach, the proventriculus, into which the gullet opens, is 
thick-walled and strongly glandular over its entire inner surface. The stomach 
proper or ventriculus, as is usual in bird stomachs, has on both sides rounded ten- 
dinous areas from which muscle fibers radiate to the margins. On one side the 
surface of the ventriculus is smoothly rounded, with the fasciae of the muscles 
radiating over it in bands that are stronger and better marked toward the lateral 
margins (not toward the anterior or posterior ends of the stomach). On the 
opposite side of the ventriculus is found a protruding lobe or pylori¢ bulb of 
large size that is bent downward; to the lower end of this is attached the duo- 
denum. This pyloric diverticulum extends down to a point level with the central 
tendon on this face of the ventriculus and by its projection interrupts the even 
radiation of the muscle on.this side. The diverticulum is set at a slight angle 
with the axis of the stomach, with the point projecting outward. As the muscle 
band from the central tendon crosses the upper margin of this bulb it becomes 
much stronger so that here it is five or six times as thick as elsewhere on the 
stomach. After crossing the lobe the muscle is reduced at once to its normal 
thickness and proceeds to its insertion at the base of the proventriculus. Exam- 
ination of the inner structure of the stomach shows that the lobe forms a small 
chamber opening from the more capacious cavity of the stomach proper. Con- 
traction of the muscle band described above would press the inner wall of the 
neck of the lobe firmly against the stomach wall opposite, closing off the small 
chamber completely, and preventing the egress of food matter. It acts therefore 
as a great valve that opens and closes as needed. The pylorus is constricted to a 
very small opening, beyond which the canal of the duodenum expands immedi- 
ately to a diameter three times greater than at the opening. 
In the following table are given outside measurements of the stomachs of 
five species of grebes taken from specimens that were well-filled with food. Stom- 
achs that are nearly empty are contracted so that they appear much smaller, or if 
crammed may be somewhat larger than the dimensions given here. 
OUTSIDE MEASUREMENTS (IN MILLIMETERS) OF STOMACHS OF GREBES 
Length Length Length 
Species of of of 
; proventriculus ventriculus pyloric bulb 
ACChMOPhOTuUus OCCIDENtAlS............0......-....000--0-0-0 30 80 25 
DUPUIFTIL DIES LOUD O CULE. «3. - 3d icon 22 boc o ad ccacteeeacesneunpececene 40 55 25 
POUL OES AI (COUP OT MICUS So 58 eon sao scnccccnnceceee 18 38 14 
MAUL OIUSHLIURLLALS ook ho ee en 25 40 13 
MAOULUMILOWS POOL C DS. -. 2. <c--kecnces-antaveceutcanSacensceencocd 28 50 24 
With a very few exceptions feathers were present in the stomachs of all of 
the birds examined. In some individuals the ventriculus was crammed with 
them ; in others the feather content was comparatively small. The pyloric lobe 
was invariably filled with a plug of feathers (except in the few stomachs that 
contained no feathers) that had been partly ground up and digested. The feath- 
ers in the ventriculus and the pyloric lobe formed two separate well-knit masses 
that usually could be distinguished without trouble in looking over the contents 
of the stomach after it had been removed. ‘The proventriculus was always empty, 
as its function in this group is to supply digestive juices, not to act as a container 
for food. The feathers swallowed were, in the main, contour feathers from the 
