FLUORIDE OF CALCIUM IN WATER. Ig3 



quite sufficient in many cases, especially if we add to the food, the drink of ani- 

 mals as a source of the ingredient in question. But when we find fossilized bones 

 containing ten or fifteen per cent, of fluoride of calcium, whilst, at the same 

 time, they have lost to a great extent their original structure, and have acquired 

 a crystalline or mineralized one, it seems highly probable that Mr Middleton's 

 beUef that water may have infiltrated that salt into them, wiU prove worthy of 

 adoption. I cannot, however, agree with him in thinking, that it is enough to 

 shew that water may bring fluoride of calcium to bones, to account for its accu- 

 mulation in them. Water, as my own experiments prove, may carry away fluo- 

 ride of calcium from osseous remains, as well as transport it to them. We reqmre > 

 to account for its detention in bones, as well as for its conveyance to them. From 

 an experiment made in the laboratory, as weU as from then' association in nature, 

 I am inclined to think that there is a double phosphate of lime and fluoride of 

 calcium, much less soluble than the latter salt is ; and that the production of this 

 compound fixes the fluoride, and prevents its abstraction by water. Further re- 

 searches will decide this point. TUl quantitative analyses of a considerable num- 

 ber both of recent and fossil bones are made, as to the proportion of fluoride of 

 calcium in them, it will be impossible to decide how far individual fossils which 

 contain that salt are to be looked upon as coming under Liebig's or Middleton's 

 explanation, or as requiring, as many probably will do, a reference to both. 

 Some, as already stated, may appear to have lost, instead of gaining, fluoride of 

 calcium, during their entombment. 



Allusion was made, in the commencement of the paper, to the possibihty of a 

 conversion of fluoride of calcium into phosphate of lime having occurred. Few 

 would more gladly see the idea of elemental transmutation realized by natural 

 phenomenon or laboratory experiment than I should do. I can find nothing, 

 however, to support it in the phenomena I have been discussing. 



In conclusion, I would observe, that physiologists wiU doubtless now be 

 tempted to speculate on the possibility of fluorine performing some essential 

 function in living animals. Its occasional absence fi-om their bones would not 

 disprove that it may be necessary for the perfection of certain organs, though not 

 for all. Quantitative analyses appear already to have indicated that the enamel 

 of teeth contains more fluorine than any other part of the body. If that result 

 shaU be conflrmed, we may suppose that, if fluorine be furnished when the deve- 

 lopment of the teeth is proceeding, it may be wanting at other periods, without 

 injury to the animal ; just as chloride of sodium must be considered as essential 

 to the healthy hfe of most creatures, though they may be deprived of it for long 

 intervals, without death ensuing. 



The small quantity of fluorine found in living structures can be counted no 

 argument against its occasional or constant importance. Quantity, is at best, 

 but a rude measure of the value of an ingredient, in relation to the necessities 



