24 OUE DOMESTIC FOWLS. 



up into blunt fragments, without having pro- 

 duced the slightest injury to t1ie gizzard. But 

 these experiments go rather to prove the ex- 

 traordinary force and grinding powers of the 

 gizzard, than to throw light upon the positive 

 use of the pebbles swallowed ; which, after all, 

 Spallanzani thought were swallowed without 

 any definite object, but from mere stupidity. 

 Blumenbach and Dr. Bostock aver that fowls, 

 however well supplied with food, grow lean 

 without them, and to this we can bear our 

 own testimony. Yet the question, what is 

 their precise effect, remains to be answered. 

 Boerhaave thought it probable that they might 

 act as absorbents to superabundant acid ; 

 others have regarded them as irritants or 

 stimulants to digestion ; and Borelli supposed 

 that they might really contribute some degree 

 of nutriment. John Hunter, in his treatise 

 "On the Animal Economy," after noticing the 

 grinding powders of the gizzard, says, in refer- 

 ence to the pebbles swallowed, " We are not, 

 however, to conclude that stones are entirely 

 useless ; for if we compare the strength of the 

 muscles of the jaws of animals who masticate 

 their food, with those of birds who do not, we 

 shall say that the parts are well calculated for 



