2 MINERAL CONSTITUENTS. 



it is a compound of two tribasic phosphates of lime^ namely 

 2Ca O, HO, PO^ + 2 (3 Ca O, POJ. It consists of 51-55 

 parts of Hme, and 48*45 of phosphoric acid. It occurs in bone, 

 blood, milk, mine, fseces, &c. 



3. Carbonate of lime forms the principal part of the skeleton in 

 the invertebrata ; it also occurs in greater or less proportion in 

 the bones of the higher animals and man, in the urine of the 

 graminivora, and in certain morbid concretions. It contains 

 56*29 parts of lime and 43*71 of carbonic acid. 



4. Phosphate of magnesia is very frequently associated with 

 phosphate of lime. In a crystalline state its formula is HO, 

 2 Mg O, PO^ + 2 HO + 12 HO. (Graham in Phil. Trans. 1837.) 

 It occurs in bone, blood, milk, shell of eggs, urine of man and 

 carnivora, intestinal concretions, fseces, &c. After the removal 

 of the water of crystallization it consists of 36*67 parts of mag- 

 nesia, and 63*33 of phosphoric acid. 



Phosphate of magnesia and ammonia, or, as it is frequently 

 termed, ammoniaco-magnesian phosphate, is a perfectly distinct 

 salt. Like the former, it is a tribasic salt, of which the 3 atoms 

 of base are, 1 atom of oxide of ammonium, and 2 atoms of 

 magnesia, with 12 atoms of water of crystallization, 10 of which 

 may be expelled without any loss of ammonia. Its formula 

 therefore is NH^ O, 2 Mg O, PO^ + 2 HO + 10 HO. Crystals 

 of this salt have been observed in the excrements in typhus and 

 other diseases ; it is also present in certain states of the m'ine, 

 and is a frequent constituent of urinary calculi. 



5. Fluoride of calcium occurs in the animal organism in very 

 minute quantity. It is much more abundant in fossil than in 

 recent bones. 



CLASS II. CONSTITUENTS USEFUL BY THEIR CHEMICAL 



PROPERTIES. 



1. Hydrochloric acid exists in the digestive fluid of man, of 

 the mammalia generally, and of birds. It has been detected 

 by Lehmann in morbid saliva. 



2. Hi/drojliwric acid has only been detected in the gastric se- 

 cretion of birds, 



3. Chloride of sodium exists in the blood, gastric juice, urine, 

 bone, cartilage, &c. 



