On the Identity of Sile.v and Oxygen. I 7 1 



there is a fair claim upon the silex as the origin of this aci- 

 dified or oxygenaled fluid, since this acid was created in the 

 very cell and immediate vicinity where silex never fails to 

 reside. 



There is commonly a large quanliiv of siliceous stones, 

 sand, and small gravel in the gizzards of birds ; in some it 

 is ill minute grains, and in others, such as ducks, geese, 

 turkeys, and other domestic poultry, it is considerable both 

 in size and quantity, according to the nature and peculiar 

 habits of each species. I have taken pieces of silex, from the 

 gizzard of a goose, some cf which weighed thirty grains, 

 and the whole contents of the gizzard were pure siliceous 

 matter, quite insoluble in diluted muriatic acid, and these 

 stones exceeded one ounce in weight. 



I have occasionally seen gizzards quite empty, and at 

 other times \ have met with them completely crammed. It 

 is absurd to say these insoluble stones are for the purpose of 

 grinding the food, and I believe no other reason has ever 

 been advanced to account for this extraordinary accumu- 

 lation. 



It has been proved, that^ independently of this silex in. 

 the gizzard, birds discharge more solid matter than the 

 amount of their food ; that their feathers grow very ra- 

 pidly, and, whatever the species of the food be, these are 

 always of the same nature ; likewise, that the chalk or car- 

 bonate of lime of the egg-shell, together with what is found 

 of the same chalky substance in the excrements, exceeds 

 in weight the whole of the lime contained in the oats, with 

 which the animal was nourished for this experiment. 



As there is a considerable difficulty in accounting for t^ome 

 most cm'ious phenomena respecting the physiology of birds, 

 in which the formation nilhne is effected, this silex of the 

 oats or food, together withvvhat is contained in the gizzard, 

 must, I should tnink, be the only source from whei\ce the 

 newly created substance, the egg-shell, can he derived. It is 

 also to be noticed, that, in these experiments, the food con- 

 tained no carbonule of lime, it is the phosphate of lime of 

 which oats are composed ; and, respecting the egg-shell, 

 nearly nine-tenths of its weight are carbonate of lime. "Are 



we 



