374 



CHARACTERS OF THE PROTEIDS. 



bones and teeth Calcium carbonate (CaC0 3 ) is associated with calcium phosphate in bone, 

 tooth, and in some fluids, but it occurs in relatively much smaller amount. It is kept to 

 solution by alkaline chlorides, or by the presence of free carbonic acid Ammonium chloride 

 (XH CI) Minute traces occur in the gastric juice and the urine. Magnesium phosphate 

 (Mg,P0 4 ) occurs along with calcium phosphate, but in very much smaller quantity.] 



IV. Free Acids. Hydrochloric acid (HC1) [occurs free in the gastric juice, but in combina- 

 tion 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, 

 chiefly in combination with soda and potash]. 



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

 constituent of haemoglobin ; copper (?), ( 174). 



248. (B) OEGANIC COMPOUNDS. I. The Albuminous or Proteid Substances. (1) 

 True Proteids and their Allies are composed of C, H, 0, N, and S, and are derived from plants 

 (see Introduction). [The formation of albumin from the elements is accomplished only by 

 plants What the chemical processes are is quite unknown. We only know that the N is in the 

 tint instance obtained from the nitric acid or ammonia of the soil. The former is probably not 

 used directly as such, but serves, perhaps, for the formation of amides or amido-acids, from 

 which, by the action of non-nitrogenous bodies, proteids are formed.] 



