SILICA. 427 



those of birds living on insects and berries 0'75-g-, and their ash 

 27$. Gorup usually found about twice as much silica in the feathers 

 of old animals as in those of the young of the same species. 



In newly grown or young feathers only traces of silica were 

 often to be found. In the pinions of the first order there was 

 twice as much silica as in the tail-feathers of the second order ; 

 and in the tail and breast-feathers there was little more than in the 

 pinions of the second order. 



Berzelius found no silica in the bones or teeth of man ; Four- 

 croy and Vauquelin* have, however, found it in the bones of chil- 

 dren, and Marchandf in those of Squalus cornubicus ; it has also 

 frequently been found in fossil bones. 



Silica has been found by Chevreulj. in sheep's wool, and by 

 Vauquelin, and more recently by Laer||, in the human hair. 

 Gorup has entered very fully into this part of the enquiry regard- 

 ing the occurrence of silica. In brown human hair he found 

 0'22-g- of silica, the ash yielding 13'89, while in the hair and wool 

 of various animals he found sometimes rather more and sometimes 

 rather less of this substance. The quantity of silica in the hair 

 appears to be altogether independent of the nature of the food. 



As silica occurs so constantly in the animal organism, it might 

 naturally be expected that we should find it in the blood, and 

 especially in that of birds. Millon^f found it in human blood ; 

 Weber** found that it amounted to 0'19-g-, in the ash of ox-blood, 

 and in hens' blood Hennebergft found 0*96. 



PoleckJJ found 7'05-g- in the ash of the white of egg ; silica has 

 also been found in the bile, urine, and solid excrements. Weiden- 

 busch found 0'36{ 7 in the ash of ox-bile; Pleisch|||| and BleyHl" de- 

 tected it in gall-stones, and Mitscherlich*** found a trace of it in the 

 saliva. Berzeliusttt was the first who discovered traces of it in 



* Ann. de Chim. T. 72, p. 282. 



t Lehrb. d. phys. Ch. 8. 97. 



I Compt. rend. T. 10, p. 632. 



Ann. de Chim. T. 58, p. 41. 



|| Ann. d. Ch. u. Pharm. Bd. 44, S. 172. 



^[ Journ. de Pharra. 3 Ser. T. 13, pp. 86-88. 



** Pogg. Ann. Bd. 76, S. 387. 



ft Op. cit. 



t Pogg. Ann. Bd. 76, S. 360 



Ibid. S. 369. 



|||| Kastn. Arch. Bd. 8, S. 300. 



flT Journ. f. pr. Ch. Bd. 1, S. 115. 



*** Pogg. Ann. Bd. 26, S. 320. 



Lehrb. d. Cliem. Bd. 9, S. 433. 



