INTRODUCTION. 19 
birds, it is much wider, and in some, as the Petrels and Ful- 
mars, enormously dilated. 
In most birds, the solution of the food is effected in the 
stomach, which is membranous, or very thin, in those that 
feed on flesh or other soft substances easily soluble ; but 
muscular in those which feed on hard substances, or on such 
as require mechanical division. When the walls of the sto- 
mach are very thin, and not capable of pounding, the bird, 
should it swallow hard or insoluble substances, as bones, 
hair, feathers, elytra, and the like, must get rid of them by 
vomiting, as is the case with Hawks, Owls, Goatsuckers, and 
Cuckoos. In cases where circumstances render it inexpe- 
dient to get rid of these hard substances, the stomach is 
muscular, though often small, and apparently intended for 
no other use than that of pounding such as may have escaped 
the action of the pro ventricular fluid; as in Petrels and 
Gulls. Birds which feed on vegetable substances, not easily 
digestible until pounded into a pulpy mass, have the sto- 
mach furnished with enormous muscles, and a hard inner 
coat, on which are two opposite grinding plates, and in them 
the cavity of the stomach is small, so that a moderate quan- 
tity only is admitted at a time. Of this kind is the sto- 
mach in Pheasants, Partridges, Grouse, Geese, and Ducks. 
This muscular grinding stomach also exists in many birds 
which feed on animal matters which are enveloped in hard 
cases, as Crustacea, insects, and the like. This is the case 
with all running and wading birds, excepting Herons, which 
feed on fishes and soft reptiles. 
In most birds, the pylorus allows nothing to pass but the 
finest pulp, so that no coarse particles are seen in the intes- 
tine. But in the vegetable-eaters, as the Badrices and the 
corresponding series of Cribratrices, the whole mass of the 
food, coarsely pounded, passes into the intestine. Their 
faeces, accordingly, resemble those of the ruminating mam- 
malia and pachydermata, which feed on similar substances. 
When the food is flesh, and therefore nutritious and easily 
