324 



ON DENTAL INCRUSTATIONS AND THE SO-CALLED "GOLD-PLATINa" 



OF SHEEP'S TEETH. 



Bv Tuos. Steel. 



For many years past there have appeared from time to time, in newspapers 

 and magazines published all over the world, statements as to the occun-enee of a 

 metallic incrustation on the teeth of sheep. The incrustation in question is usu- 

 ally found more or less thickly coating the sides of the molar teeth, and. being 

 fre(iuently of a shining, yellowish, metallic appearance, has been popularly 

 attributed to gold supposed to have been derived from particles of that metal 

 scattered about the pastures. So deeply-rooted is the popular belief that the 

 incrustation consists of gold, my friend, Mr. J. H. Campbell, informs me that 

 persons have brought jaws of sheep to the Eoyal ilint. Sydney, with a view to 

 selling them for the supposed adherent gold. Quite recently, it was most confi- 

 dently asserted by correspondents in Xature* that the incrustation consisted of 

 iron pyrites, and various fantastic theories were put forward to account for the 

 presence of this substance in such a situation. 



In 1905 Professor Liversidge exhibited at a meeting of the Royal Society of 

 New South Wales! part of a sheep's jaw. heavily coated with yellow metallic- 

 looking deposit, and read a descriptive note with a qualitative analysis, clearly 

 showing the true nature of the substance to be a deposit derived from the saliva, 

 and that the metallic appearance was due to the refraction of light by the over- 

 lapping edges of the thin lamellae of the deposit. Again, in .Tuly. 190.5. the same 

 gentleman exhibited and explained the deposit at a meeting of the Sydney section 

 of the Society of Chemical Industry. Similar specimens were exhibited by 

 Horan to the New South Wales Naturalists' Club in 1013. t 



As will be shown in this paper, the presence of such deposits is by no means 

 confined to the teeth of sheep, but is a common occuiTence on those of a very large 

 variety of animals, including man. It is, in fact, a dental calculus analogous to 

 those occurring in the urinary tract. 



The earliest account of the true nature of dental incrustations witli which T 

 have met, occurs in the Annals of Philosoi-)hy.§ In the course of a series of 

 articles entitled "General Views of the Composition of Animal Fluids," Rerzelius 

 gives a correct explanation of the nature of the deposit from human teeth, and his 

 analysis of a specimen, which will be quoted further on. 



In 1834, Dr. G. Bennett || re(!ords having observed a layer of "metallic sub- 

 stance" incrusting the teeth of kangaroos, and correctly diagnosed it as "tartar" 



•Nature, xcix., 1917, pp.2fi4, 284, 290. .'itX); c, 1917, p.l06. 



+Journ. Roy. Soc. N.S.Walt-s, xxxix., 190.'), p.3:ij .also Chem. News, xcii., 1905. p. 11.5; 

 .Tour. Soc. Chem." Tnd.. xxiv., 1905, p.lO.TO. 



tAustralian N.ituraliat, ii.. 191,^, pp!l74, 187. 

 §Thoinson's Ann. Phil., ii., 1814. p..'i80. 

 ilWamWinors in New South Wales, i., 1834. p. 294. 



