The Gizzard. 23 



the mill-like action of the gizzard, has been a matter of 

 difference among various physiologists, and many experi- 

 ments, with a view to elucidate the subject, have been 

 undertaken. It was sufficiently proved by Spallanzaiii that 

 the digestive fluid was incapable of dissolving grains of 

 barley, &c., in their unbruised state ; and this he ascertained 

 by filling small hollow and perforated balls and tubes of 

 metal or glass with grain, and causing them to be swallowed 

 by turkeys and other fowls ; when examined, after twenty- 

 four and forty-eight hours, the grains were found to be 

 unaffected by the gastric fluid ; but when he filled similar 

 balls and tubes with bruised grains, and caused them to be 

 swallowed, he found, after a lapse of the same number of 

 hours, that they were more or less dissolved by the action 

 of the gastric juice. In other experiments, he found that 

 metallic tubes introduced into the gizzard of common fowls 

 and turkeys, were bruised, crushed, and distorted, and even 

 that sharp-cutting instruments were broken up into blunt 

 fragments without having produced, the slightest injury to 

 the gizzard. But these experiments go rather to prove the 

 extraordinary 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 ques- 

 tion, what is their precise effect ? remains to be answered. 

 Boerhave 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." 



Sir Everard Home, in his "Comparative Anatomy," 

 says: "When the external form of this organ is first 

 attentively examined, viewing that side which is anterior in 

 the living bird, and on which the two bellies of the muscle 

 and middle are more distinct, there being no other part to 

 obstruct the view, the belly of the muscle on the left side is 



