ON THE DIGESTIVE FUNCTION, ETC. 



i37 



sent to the gizzard or proper stomach, whose muscular mechanism, in 

 conjunction with its gastric juice, soon comminutes it into the most impal- 

 pable pulp. There are several kinds, however, that, like the ostrich, en- 

 deavour to assist the muscular action by swallowing pebbles or gravel ; 

 a^me of which find this additional aid so indispensable, that they are not 

 TU)le to digest their food, and grow lean, without it. Spalanzani attempted 

 to prove that these stones are of no use, and are only swallowed by acci- 

 dent ; but their real advantage has been completely established by Mr. J. 

 Hunter, who has correctly observed, that the larger the gizzards, the larger 

 are the pebbles found in them. In the gizzard of a turkey he counted two 

 hundred ; in that of a goose, a thousand. 



Reaumur and Spalanzani have put the prodigious power of this muscu- 

 lar stomach to the test, by compelling geese and other birds to swallow 

 needles, lancets, and othef-hard and pointed substances ; which, in every- 

 experiment, were found, a few hours afterwards, on killing and examining 

 the animal, or on its regorging them, to be broken off and blunted, with- 

 out any injury to the stomach whatever. 



Yet, as all animals are not designed for all kinds of food, neither the 

 force of the strongest muscular fibres, nor the solvent power of the most 

 active gastric juice, will avail in every instance. The wild-boar and the 

 vulture devour the rattlesnake uninjured, and fatten upon it ; but there arc 

 many kinds of vegetables which neither of these are capable of digesting. 

 The owl digests flesh and bone, but cannot be made to digest grain or 

 bread ; and in one instance died, under the experiments of Spalanzani, 

 when confllned to vegetable food. The falcon seems as uttle capable of 

 dissolving vegetables ; yet the eagle dissolves bread and bone equally ; and 

 wood- pigeons may, in like manner, be brought to live, and even to thrive, 

 on flesh-meat. The procellaria pelagica^ or stormy petril,* lives entirely on 

 oil, as the fat of dead whales ai^d other flshes, whenever he can get it : and 

 if not, converts every thing he swallows into oil. He discharges pure oil 

 from his mouth at objects that offend him ; and feeds his young with the 

 same substance. This is the most daring of all birds in a tempest, though 

 not more than six inches long. As soon as tlie clouds begin to collect, he 

 quits his rocky covert, and enjoys the gathering and magnificent scenery ; 

 he rides triumphantly on the whirlwind, and skims with incredible velocity 

 the giddiest peaks, and deepest hollows of the most tremendous waves. 

 His appearance is a sure presage of foul weather to the seaman. 



There are some tribes of animals that appear capable of subsisting on 

 water alone, and a few on mere air, incapable as these substances seem to 

 be, at first sight, of affording any thing like solid nutriment. Leeches and 

 tadpoles present us with fauiiliar proofs of the former assertion, and there 

 are various kinds of fishes that may be added to the catalogue. Rondelet 

 kept a silver fish in pure water alone for three years ; and at the end of that 

 period it had grown as large as the glftss globe that contained it. Several 

 species of the carp kind, and especially the gold-fish, have a similar power ; 

 and even the pjjce, the most glutinous, perhaps, of the whole class, will 

 both five and thrive upon water alone in a marble basin. 



The bee, and various other insects, derive their nutriment from the nectar 

 and eflOluvium of flowers. So also does the trochilus genus, or humming- 

 bird, which appears to be the connecting Unk between the two classes ; 

 buzzing like the bee itself with a joyous hum around the blossom on which 

 it lights; and in one of its species, t. minmiis. not ex^zeeding it in size, and 

 only weighing from 20 to 45 grains. 



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