13 



8 The Bird 



That this is something more than an abnormal con- 

 dition brought about by artificial means is proved by 

 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 very 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 histor}^ of the development of this organ may 

 be traced in various living species, from the soft mem- 

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

 which forms the gizzard of certain Fruit-pigeons. These 

 birds feed on nutmegs and other very hard, almost stony 

 nuts, and to enal)le 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 likely to find. 



What a boon to a business 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 

 bird, is provided with a gizzard, which, like that of a 

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

 dons, and no less than five pounds of grinding-stones 

 have been found in one of these reptiles. 



Many interesting adaptations are found in the stom- 

 achs of birds, made necessary by special requirements 

 in the diet. As an instance of this, the snake-bird has 



