466 



tions of previous analysts on the occurrence of a dissolved fluoride in 

 fresh water, and for the first time announces its direct discovery in 

 sea-water, where Middleton and Dana had independently anticipated 

 its presence, after finding it invariably in the shells of marine mol- 

 lusca and in corals. The fourth section, entitled " Of the presence 

 of Fluorine in Minerals," does not call for special notice. The fifth 

 entitled " Of the presence of Fluorine in Plants," confirms the re- 

 sults of Will of Giessen as to the existence of this element in the 

 ashes of vegetables, and draws attention to plants and to water as 

 the media by which fluorides may be transferred from the soil to 

 animals. The sixth section, entitled " Of the presence of Fluorine 

 in Animals," commences with the statement, " As thei'e exists, then, 

 a twofold soui'ce of fluorine for animals, we may anticipate its occur- 

 rence in various parts of their structure;" and thereafter announces, 

 in opposition to the negative results of Dr Rees, my confirma- 

 tion of the observation of Berzelius, that a fluoride is present in hu- 

 man urine, — a result which the great Swedish chemist hailed with sa- 

 tisfaction before his death*, although M. Nickles seems to think that 

 he has been the first to confirm the original assertion. The paper 

 then proceeds to state, — " It could not be doubted, after the facts I 

 have detailed, that fluorine would be found in the two great for- 

 mative liquids of the animal body, blood and milk ; I have found it 

 in both. So far as I am aware, it has hitherto been overlooked in 

 all the analyses that have been made of these liquids ; probably it 

 has not been sought for. I employed the blood of the ox, and in 

 two cases obtained markings on glass which only became visible 

 when breathed upon, but ai-e then quite manifest. In the third, the 

 glass was distinctly, though faintly, corroded." 



The concluding part of this section is occupied with a criticism of 

 the declaration of Treviranus, that the gastric juice of birds contains 

 hydrofluoric acid ; the final sentence being, " We may now look fur 

 fluorine in all the animal fluids." 



I merely name the title of the seventh section, which is headed 

 " Of the presence of Fluorine in Fossil Bones, and its relation to 

 Animal Life." 



In the summer of the same year, 1846, I ascertained the ex- 

 tent to which pure water dissolves fluor-spar, namely, 0*26 grains 



* Juhres-Bericht, von Jacob Berzelius, 1818, p. 164, which contains a general 

 comment on my researches of 1846. 



