176 SOURCE OF FLUORINE IN FOSSIL BONES. 



for I have been able in several instances to obtain a perma- 

 nent delineation of the characters traced without the presence 

 of fluorine. In these cases it is caused by the action of the 

 vapors of either sulphuric or hydrochloric acid upon certain 

 kinds of glass that contain a large quantity of metallic oxides, 

 or upon glass the surface of which has been altered by the 

 action of the air. There is, however, no apparent corrosion in 

 these cases. 



The existence of fluorine in fossil bones, and its doubtful— 

 or, as some say, absolute — non-existence in those of recent 

 animals, have induced MM. Girardin and Preisser to conclude 

 that it did not belong originally to the bones of fossil animals, 

 but has found its way there by infiltration after their death; 

 and they appear to have come to this conclusion without hav- 

 ing examined the chemical character of the formations from 

 which the various bones were taken. 



I have had an opportunity of throwing some light upon 

 this subject from the examination of two bones taken from the 

 same calcareous deposit and within two feet of each other, the 

 one cellular and the other compact. The cells of one of these 

 bones were filled with small concretions of calcareous matter, 

 evidently arising from the infiltration of some of the material 

 forming the bed in which they lie. These concretions, it would 

 seem, ought certainly to contain a portion of whatsoever matter 

 had been infiltrated, as all infiltrations must have passed in 

 together. These concretions, carefully detached from the bone, 

 were examined especially for fluorine, but not the. slightest 

 trace was found; while on the contrary a very small quantity 

 of the compact part of the same bone gave decided indications 

 of the presence of this substance. This fact must certainly 

 lead to the conclusion that the fluoride of calcium in the body 

 of the bone was not infiltrated; for had it been otherwise it 

 would have been associated with matter known to be infiltrated, 

 as the calcareous nodules. 



The same cellular bone was examined as a whole — that is to 

 say, without detaching the calcareous matter — in comparison 

 with the compact bone from the same locality; and in the 

 former there was found less fluoride of calcium than in the 

 latter, contrary to what would have been the case had this 

 fluoride been infiltrated. 



