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 proventicular fluid ; as in Petrels and 

 Gulls. Birds which feed on vegetable substances, not easily 

 digestible until pounded into a pulpy mass, have the stomach 

 furnished with enormous muscles, and a hard inner coat, on 

 which are two opposite grinding plates, and in them the ca- 

 vity of the stomach is small, so that a moderate quantity 

 only is admitted at a time. Of this kind is the stomach 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 Radrices and the 

 corresponding series of Cribratices, 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 



