TASTE OF GRANIVOROUS BIRDS. 123 



as we have already mentioned, has been very diffe- 

 rently explained by naturalists. These stones were 

 considered by the Italian naturalist Csesalpinus, rather 

 as medicinal, than as a common auxiliary to digestion ; 

 while Boerhaave supposed them to act as absorbents 

 for any superabundant acid in the stomach ; and 

 Whytt of Edinburgh supposed the irritation, which 

 he inferred them to produce, useful as a stimulant to 

 the obtuse, almost insensible, coats of the gizzard *. 

 Borelli again formed the very extravagant idea that 

 the stones in question contributed directly to nutri- 

 tion, an opinion which is refuted by the experiments 

 of Redi, who, having shut up two capons with nothing 

 but water and little pebbles for food, found that they 

 drank much water, but died, one in twenty, the other 

 in twenty-four days, neither of them having swallowed 

 a single storief. 



An opinion little less fanciful adopted by Blumen- 

 bach ascribes to the stones the especial purpose of 

 killing the grains of corn, which, while capable of 

 germinating, would resist the action of the digestive 

 fluid J. This requires no refutation ; but it has been 

 supposed to be partially corroborated from the similar 

 circumstance of pebbles being swallowed by the 

 pangolin (Manis pentadactyla) ; for as the food of 

 this animal consists of insects swallowed entire, the 

 pebbles have been thought necessary for the purpose 

 of crushing the insects and depriving them of life, so 

 as to render them capable of being digested . 



Others have supposed these pebbles intended to 

 sheath the gizzard in order to enable it to digest, or 

 at least to break down into small fragments, the hard 



* Phys. Essays, 8vo. Edinb. 1766. 

 f Esperienze, p. 84; Osserv. p. 91-2. 



J Comp. Anat. 100. 

 Bostock, Physiol. iii. 408, note. 



