XIV 
INTRODUCTION. 
fluid. But the stomachs of birds of prey, and of the piscivorous tribes, 
differ essentially from those of the granivorous kinds ; as they neither pos- 
sess their strength, their firmness of texture, their figure, nor their power- 
ful action. Composed of a thin membranous substance, in a sack-like 
form, mthout those vigorous and prodigious muscles that distinguish 
granivorous birds, nature has supplied the want of mechanical power, by 
this tasteless solvent, called, as we have before stated, the gastric fluid, of 
all animal menstrua the most active, which, in these kinds, dissolves 
readily the fleshy fibres taken into the stomach, and corrodes and concocts 
even bones, into a sort of gelatinous matter. Although thus powerful in 
its action on substances which constitute the proper food of the animal, 
yet, so confined are its effects, that it is perfectly harmless on the living 
fibres that enclose it ; and, in the carnivorous kinds, even tender vegeta- 
bles, and delicate fruits, have been found to remain ® many hours under its 
action, without undergoing diminution. Wonderful, indeed, is this extraor- 
dinary property of solution ; for, while decomposing those things which are 
subject to its operation, it, at the same time, neutralizes the process of fer- 
mentation, and resists the dissolving heat of putrefaction. Nature has 
given to these birds the power of disgorging such substances as are not 
operated upon by the gastric Juice ; else, as the oesophagus is larger than 
the intestinal canal, by which the food is emitted, when such substances 
are of great size, they would not pass off' in an undissolved state. Many 
birds possess, as we have before-mentioned, a secretory organ, full of 
glands, formed by the expansion of the oesophagus, and situated imme- 
® I have frequently made similar experiments on various kinds of hawks. I have given 
twenty grains of barley to a Kestril, which remained upwards of thirteen hours in its stomach, 
and which were disgorged without any diminution. In fact, they were swollen, and puffed up a 
little. I took eight of these grains, as soon as they were thrown up, and divided them nearly 
into two parts longitudinally, so as to expose the farinaceous substance to the action of the gastric 
fluid ; in about eleven hours they were again vomited, nor could I perceive they had lost any 
thing of their weight. It should be observed, that it was fed with small birds, none of the bones 
of which it brought up in the pellets it disgorged. To prevent the possibility of its discharging 
them without discovery, it was confined in a cage. 
