444 THIRD CLASS OF MINERAL CONSTITUENTS. 



further. But since the iron is of especial importance in the animal 

 body, we cannot wonder at its occurrence in the milk and in the 

 egg. If we find iron in the bile, its occurrence there is easily 

 explained, if we adopt the view that this fluid is for the most part 

 produced from the destruction of the blood-corpuscles. 



The fluid and solid articles of food contain so much iron that a 

 portion of it is always thrown off with the solid excrements. 

 Nature has provided that the animal organism shall receive the 

 necessary quantity of this essential metal with every kind of food. 



THIRD CLASS OF MINERAL BODIES. 



ALKALINE SULPHATES. 



Sulphates occur in most of the animal fluids, with the excep- 

 tion of the urine, in extremely small quantities ; and, indeed, in 

 several, as, for instance, the milk, the bile, and the gastric juice, 

 they are altogether absent. They are also contained in compara- 

 tively minute quantities in the blood. Hence it may be concluded 

 that these salts are of no essential use in the animal organism ; 

 a view which is confirmed by the fact that as soon as they are 

 taken into the body, they are as rapidly as possible eliminated 

 either with the solid or the fluid excrements. On the other hand, 

 it is worthy of remark, that v. Bibra* found considerable quantities 

 of soda in the bones of reptiles and fishes. 



Berzeliusf and Simon J found no sulphates in the milk, and 

 Braconnot and Berzelius|| also failed to detect them both in the 

 gastric juice, and in the bile of man and the ox. 



If we treat the dry residue of the serum of the blood, milk, 

 saliva, bile, &c., with spirit, till it ceases to extract anything addi- 

 tional on boiling, and if we then extract the insoluble residue with 

 water, precipitate the aqueous solution with a little tannic acid, eva- 



* Chem. Unters. liber die Knochen u. Zahne. S. 226 u. 242. 



t Lehrb. der Chem. Bd. 9, S. 095. 



J Frauenmilch. S. 43. 



Op. cit. 



II Jahresber. Bd. 16, S. 379. 



