138 The Bird 



That this is something more than an al)normal con- 

 dition brought about 1)}' artificial means is jjroved })y 

 the fact that in the Orkney Islands the wild gulls feed 

 in winter, spring, and summer on fish, and at this time 

 are gizzardless, but in the fall they change to a diet of 

 corn and develop a ver}- respectable gizzard. So we 

 see that this organ, apparently so independent in func- 

 tion and individual in appearance in many birds, is in 

 reality only a physiological change from the stomach 

 proper. 



The history of the development of this organ may 

 l)e traced in various living species, from the soft mem- 

 branous sac of a fish-eating bird to the knot of tendons 

 wliicli forms the gizzard of certain Fruit-pigeons. These 

 birds feed on nutmegs and other ver}' hard, almost stony 

 nuts, and to enable the bird to crush these, the lining of 

 the gizzard is covered with several score of conical pro- 

 jections, horny in consistence. These are probably the 

 nearest approach to "hen's teeth" we are likeh' to find. 



What a boon to a lousiness man who indulges in a 

 daily "fireman's lunch," if his masticatory function 

 could be an internal and unconscious one, as in a bird! 



A crocodile, which has so much in common with a 

 ])ird, is ])rovided with a gizzard, which, like that of a 

 chicken, is round, nuiscular, and has two great side ten- 

 dons, and no less than five ]wunds of grinding-stones 

 have been found in one of these reptiles. 



Many interesting adaptations are found in the stom- 

 achs of ])irds, made necessary by special requirements 

 in the diet. As an instance of this, the snake-])ir(l has 



