500 SALTS, ACIDS, AND BASES IN THE BODY. 



much less extent in the other solids and fluids of the body. Amongst secretions, 

 milk contains relatively the largest amount (2 '72) per cent. In milk it is neces- 

 sary for forming the calcareous matter of the bones of the infant. It gives bones 

 their hardness, solidity, and rigidity. It is chiefly derived from the food, and as 

 only a small quantity is given off in the excretions, it seems not to undergo rapid 

 removal from the body.] 



Sodium phosphate (PNa 3 4 ), acid sodium phosphate (PNa 2 H0 4 ), acid 

 potassium phosphate (PK 2 H0 4 ). [The sodium phosphate and the 

 corresponding potash salt give most of the fluids of the body their 

 alkaline reaction. The alkaline reaction of the blood-plasma is partly 

 due to alkaline phosphates which are chiefly derived from the food. 

 The acid sodium phosphate is the chief cause of the acid reaction 

 of the urine. A small quantity of phosphoric acid is formed in the 

 body owing to the oxidation of " lecithin " which contains phosphorus, 

 and also forms an important constituent of nerve-tissue.] 



Sodium carbonate (Na 2 C03) and sodium bicarbonate (NaHCOs) [exist in small 

 quantities in the food, and are chiefly formed in the body from the decomposition 

 of the salts of the vegetable acids. They occur in the blood-plasma, where they 

 play an important part in carrying the CO 2 from the tissues to the lungs.] 



Sodium and potassium sulphates (NaS0 4 , and K 2 S0 4 ) [exist in very small 

 quantity in the body, and are introduced with the food, but part is formed in the 

 body from the oxidation of organic bodies containing sulphur.] 



[Potassium chloride (KC1 2 ) is pretty widely distributed, and it occurs specially 

 in muscle, coloured blood-corpuscles, and milk. Calcium fluoride (CaFl 2 ) occurs 

 in small quantity in bones and teeth. Calcium carbonate (CaC0 3 ) is associated 

 with calcium phosphate in bone, tooth, and in some fluids, but it occurs in rela- 

 tively much smaller amount. It is kept in solution by alkaline chlorides, or by the 

 presence of free carbonic acid.] 



Ammonium chloride (NH 4 C1). [Minute traces occur in the gastric juice and 

 the urine.] 



Magnesium phosphate (Mg 3 P0 4 ) [occurs in the tissues and fluids of the body 

 along with calcium phosphate, but in very much smaller quantity.] 



IV. PreeAcids. Hydrochloric acid (HC1) [occurs free in the gastric juice, but 

 in combination with the alkalies it is widely distributed as chlorides.] Sulphuric 

 acid (H 2 S0 4 ) [is said to occur free] in] the saliva of certain gasteropods, as Dolium 

 galea, In the body it forms sulphates, being chiefly in combination with soda and 

 potash.] 



V. Bases* Silicon as silicic acid (Si0 2 ) ; manganese, iron, the last forms an 

 integral constituent of the blood pigment ; copper (?), p. 352. 



248. (B.) Organic Compounds. 



I. THE ALBUMINOUS OR PROTEID SUBSTANCES. 

 1. Froteids and their Allies. 



r6teids and their allies are composed of C, H, 0, N, and S, and are derived 

 from plants (see Introduction). 

 [According to Hoppe-Seyler their general percentage composition is 



O. H. N. C. S. 



From . . . 20-9 6'9 15 -2 51 '5 0'3 

 to .... 23-5 to 7'3 to 17'0 to 54*5 to 2-0.] 



