Tresence of Fluorine in Blood and Milk. 229 



Vitriol were added at considerable intervals, and the contents 

 of the basin occasionally stirred. The glass, which was 

 cooled on the upper surface by the frequent renewal of a 

 ptratum of cold water, slowly became dim, and slightly opal- 

 descent where the letters were traced, in consequence, no 

 doubt, of the separation of silica, for the letters appeared 

 'deeply etched when the wax was cleaned off. From the large 

 scale on which the experiment was conducted, and the sim- 

 plicity of the process followed, the evidence in favour of the 

 presence of fluorine in the blood of the ox seems unexcep- 

 tionable ; and it cannot be doubted that the blood of other 

 animals will be found to contain the same element. I have 

 detected it in the blood of the horse. I presume it to be pre- 

 "Bent in the state of fluoride of calcium, and that its amount 

 is very small, but I have not attempted its quantitative de- 

 termination. 



Milk was examined in a similar way, but its reduction to 

 ashes was much more easily effected than that of blood. I 

 failed, however, to obtain other than the faintest indications 

 of fluorine from the ashes of about 20 imperial pints of cows' 

 milk. It was from a town dairy, and left a suspiciously 

 small residue of solid matter. The main cause of the failure, 

 however, I believe to have been the neglect to deprive the 

 milk-ashes of the chlorides they contained. The experiment 

 "was repeated, with nine imperial pints of rich milk from a 

 country farm, the ashes of which were washed with a mini- 

 mum of water, dried and treated like those of blood. The 

 vapour which they evolved, etched glass distinctly. The 

 ashes of 12 lbs. of new skim-milk cheese made this spring, 

 treated in the same way, occasioned deep etching of glass. The 

 ashes of four imperial pints of whey treated in the same way, 

 have barely marked glass, so as to shew the faintest outlines 

 when breathed upon. In all probability the fluoride of cal- 

 cium is associated with the phosphate of lime present in milk, 

 and when the latter is coagulated, separates along with the 

 caseine. 



I need not remind the Section that fluorine was long ago 

 detected in another of the animal fluids, namely, urine, as 

 well as in the skeletons, both external and internal, of, I may 



