THE ANATOMY OF A BIBD 



21 



Gizzard and Alimentary Canal. 



The gizzard (fig. 14) of the fowl is simply a part of the stomach 

 which has especially hard and muscular walls, the other half re- 

 maining soft in texture ; this latter is termed the proventriculus, and 

 into it open the mouths 

 of glands which secrete 

 the digestive juice of the 

 stomach. But the mus- 

 cular part of the stomach 

 — the gizzard — has to 

 grind down the fre- 

 quently hard food of the 

 bird, so it has not 

 merely a strong wall 

 made of muscle, but 

 also a very tough lining ; 

 the whole organ, there- 

 fore, forms a highly 

 efficient mechanism for 

 crushing and grinding 

 the seeds and other hard 

 vegetable food which is 

 swallowed. It is ren- 

 dered more useful still 

 for this purpose by the 

 pebbles which every 

 bird takes care to swal- 

 low. The true and 

 singular stories about 

 the varied contents of 

 an Ostrich's stomach are 



founded upon the fact that, like other birds, it picks up stones, and 

 with them occasionally other objects. But all birds do not possess a 

 hard gizzard ; in Hawks and fish-eating birds the walls are thinner, 

 and the organ is flaccid instead of being rigid. By a very curious and 

 unique exception certain Tanagers, a race of large, often bright- 

 coloured, American, finch-like birds, have nothing at all that can be 

 compared to the gizzard of other birds • this part of the ahmentary 



Fig. 14. — Gizzakd of Swan. 



0, orifice of duodenum ; 

 a, end of proventriculus ; cd, muscular part of gizzard. 



