78 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 



and early life than in adult life. This is illustrated by the following 

 table : 



Na 2 K 2 1 Na,0 K 2 



Babbit's embryo . 2'183 2 '605 



Babbit 14 days old 1-630 2'967 



Kitten 1 day 2'666 2-691 



Cat 19 davs 2'285 2'790 



Cat 29 days old 2-292 2'684 

 Dog 4 2-589 2-G67 

 Adult mouse . 1-700 3-280 



This fact is probably due to the larger amount of cartilage (rich in 

 soda salts) and the smaller amount of muscle (rich in potash salts) in 

 early life as compared with the adult condition. 1 



Various phosphates of sodium and potassium are found in the blood, 

 lymph, urine, and other secretions. 



Sodium carbonate and bicarbonate occur in the food, and originate 

 in the body from the salts of vegetable acids (tartaric, citric, etc.). 



Sodium and potassium sulphate exist in smaller quantities in the 

 body. Only minute quantities of these salts are introduced with the 

 food; they are chiefly formed by the oxidation of proteids and other 

 organic substances containing sulphur. 



Ammonium salts. Minute traces of ammonium chloride are found in 

 the urine. The urine of reptiles and birds is largely composed of 

 ammonium urate. Small quantities of this salt, and also of ammonio- 

 magnesic phosphate, are found in human urine. Ammonium carbonate 

 is formed from urea in decomposing urine. 



Calcium salts. About three-quarters of the total mineral solids in 

 the body consist of calcium phosphate, Ca.,(l ) 4 )., ; this is because of the 

 great preponderance of this salt in bone. Other calcium salts occurring 

 in bone, dentine, and enamel are the carbonate, sulphate, and fluoride. 

 Calcium phosphate, urate, and oxalate, are found in the urine. Most 

 tissues contain small quantities of the phosphate and carbonate. Egg 

 shells, the shells of Crustacea, coral, and otoliths consist chiefly of 

 carbonate of lime. 2 



Magnesium salts. Magnesium phosphate (Mg 3 (P0 4 ) 2 ) occurs in the 

 tissues along with the calcium phosphates (Ca 3 (P0 4 ) 2 and CaH 4 (P0 4 ) 2 ) 

 but in smaller amount. It occurs also in the urine. Ammonio-magnesium 

 or triple phosphate (NH 4 MgP0 4 +6H 2 0) is also often found in decom- 

 posing urine. Magnesium palmitate and stearate are found in the faeces. 



Iron is an important constituent of the blood pigment. The blood 

 of an adult contains 3 grms. of iron. Small quantities are found in 

 other liquids of the body (chyle, lymph, bile, milk, urine, gastric juice) ; 

 it is also contained in the black pigment of the skin and hair, and of 

 melanotic sarcomata. A small quantity of ferric sulphide is found in 

 the faeces, and small quantities of iron are found in both liver and 

 spleen. 3 It is present in the tissues in organic combination with nuclein 

 (see p. 68). 



Copper is found in two proximate principles, hsemocyanin, the blue pig- 

 ment of the blood of many invertebrates (crustacea, cuttle-fishes, scorpions, 

 etc.), and in the pigment, turacin, of birds' feathers. Small quantities of this 

 metal, and also of aluminium, manganese and lead, may occur accidentally in 



1 Bunge, Ztschr. f. physiol. Cftem., Strassburg, Bd. xiii. S. 399. 



2 On excretion and absorption of lime see Rey, Chem. Centr.-EL, Leipzig, 1895, Bd. ii. 

 S. 55, 837. 



8 For data concerning the amount of iron in foods, see Stockman, Journ. Physiol., 

 Cambridge and London, 1895, vol. xviii. p. 484 ; 1897, vol. xxi. p. 55. An ordinary 

 daily diet contains 9-10 mgrms. of iron. 



