INORGANIC COMPOUNDS. 79 



other parts, being taken in with the food, 1 and not excreted at once with the 

 faeces, but deposited in some tissue or organ. Drugs and poisons (mercury, 

 arsenic) may be similarly deposited. 



Silica. A minute quantity of silica exists in the blood, urine, bones, 

 hair, and other parts. 



Phosphates. The amount of phosphoric acid given in analyses of 

 the ash of animal structures is not always correct, since a certain 

 quantity is obtained during the process of incineration, from the decom- 

 position of organic compounds, which, like lecithin, contain phosphorus. 



The phosphoric acid which occurs in mineral compounds in the body 

 is derived in part directly from the food, and in part from the metabolism 

 of lecithin and nuclein. It unites with soda, potash, lime, and magnesia 

 to form the various phosphates already alluded to. An adult man 

 eliminates by the kidneys 2 '5 to 3 '5 grins, of phosphoric acid daily. 

 Carnivora eliminate phosphates chiefly by the kidneys, herbivora chiefly 

 with the faeces. 



Carbonates. The presence of carbonates in the ash of animal matters 

 is partly derived from the decomposition of organic compounds. 

 Alkaline carbonates and bicarbonates are, however, found in blood, 

 urine, lymph, saliva, etc. 



Sulphates. These also may be partly formed during the process of 

 incineration, from proteids and other organic compounds containing 

 sulphur. The sulphuric acid in the urine is in part combined as ordinary 

 sulphates, in part as ethereal sulphates. It is derived to a small extent 

 from the food, but chiefly from the metabolism of proteids, the amounts 

 of sulphuric acid and urea in the urine running parallel. 



1 Karl B. Lehmann (Arch. f. Hyg., Miinclien u. Leipzig, Bd. xxiv. S. 1, 18, 72) 

 states that in an ordinary diet we take 20 mgrms. of copper daily, and if preserves are much 

 used, it may rise to over 300 mgrms. per diem ; more than 120 mgrms. appears to be harmful. 



