OF NATURAL HISTORY. 229 



tion of the firmeft food, or the hardeft foreign fubftance, contrary 

 to the opinion of many anatomifts and phyfiologifts, as well an- 

 cient as modern. 1 will not, however, deny, that, when put in 

 motion by the gaftric mufcles, they are capable of producing fome 

 effe£l on the contents of the ftomach.' 



The celebrated Mr John Hunter, in his Obfervations on Digejiion*^ 

 fairly quotes the modeft conclufion of Spalanzani, But he infifts 

 that ftones are extremely ufeful in the comminution of grain, and 

 other fubflances, which conflitute the food of many fowls. ' In 

 confidering,' Mr Hunter remarks, ' the ftrength of the gizzard, 

 and its probable effedts when compared with the human ftomach, 

 it muft appear that the gizzard is, in itfelf, very fit for trituration. 

 We are not, however, to conclude, that ftones are entirely ufelefsj 

 for, if we compare the ftrength of the mufcles of the jaws of ani- 

 mals who maftigate their food, with thofe of birds who do not, 

 we fhall fay, that the parts are well calculated for the purpofe of 

 maftication ; yet we are not from thence to infer, that the teeth 

 in fuch jaws are ufelefs, even although we have proof that the 

 gums do the bufinefs when the teeth are gone. If ftones are of 

 ufe, which we may reafonably conclude they are, birds have an 

 advantage over animals having teeth, fo far as ftones are always 

 to be found, while the teeth are not renewed. — If we conftantly 

 find in an organ fubftances which can only be fubfervient to the 

 funftions of that organ, fliould we deny them that ufe, although 

 the part can do its office without them ? — The ftones affift in 

 grinding down the grain, and, by feparating its parts, allow the 

 gaftric juice to come more readily in contadt w^ith it.' 



The. 



• Page 15,6^,. 



