SULPHOCYANATE OF SALIVA. 345 



pathological conditions, but are not normal constituents. Grape-sugar 

 and bile pigments are never found even in the severest cases of diabetes 

 or icterus. 1 



Inorganic constituents. These consist of salts of the alkalies (chiefly 

 sodium) and alkaline earths ; principally as chlorides, but also as 

 phosphates and carbonates. 2 Calcium carbonate often separates from 

 saliva, as a thin surface film, or as a cloudiness in the fluid on standing ; 

 this is due to the escape of carbon-dioxide by which the calcium was 

 held in solution as bicarbonate. A precipitation of the calcium of the 

 saliva, partially as carbonate and partially as phosphate, in the ducts of 

 the salivary glands, often gives rise to salivary concretions ; and a similar 

 deposit, mixed with phosphate and traces of silica, forms the tartar 

 of teeth. 



Sulphocyanate of saliva. Treviranus, 3 as early as 1814, observed 

 that when a dilute solution of ferric chloride is added to saliva a reddish 

 coloration is obtained. This was even before sulphocyanic acid was 

 known chemically, and Tiedemann and Gmelin 4 afterwards proved that 

 the effect was due to the presence of a sulphocyanate. 



The amount of sulphocyanate is not large. Oehl states it as equivalent to 

 '000 16-0 '0084 per cent., estimated as potassium sulphocyanate, and Munk 

 as equivalent to O'Ol per cent, sulphocyanic acid, or 0'014 per cent, of 

 sodium sulphocyanate. 5 The presence of a sulphocyanate in saliva may be 

 demonstrated qualitatively in several ways (1) A very greatly diluted and 

 slightly acidulated solution of ferric chloride is added drop by drop to saliva, 

 when a reddish coloration is obtained, if sulphocyanate is present in normal 

 quantity; the colour disappears on adding mercuric chloride. This test is 

 difficult to obtain. (2) A filter paper is dipped in a weak solution of ferric 

 chloride, containing a trace of hydrochloric acid, and then allowed to dry, when 

 it should have only a faint amber colour. On such test paper a drop of saliva 

 produces a reddish stain. 6 (3) Filter paper is impregnated with tincture of 

 guaiacum, and then drawn through a solution of 0'05 per cent, copper sulphate. 

 On such paper, saliva containing sulphocyanate causes a blue stain. 7 (4) Saliva 

 is treated with iodic acid, when iodine is set free ; this in turn is treated with 

 starch paste, when the blue compound of starch and iodine appears. This is 

 said to be an exceedingly delicate reaction, showing a most minute trace of 

 sulphocyanate, and not being produced by saliva free from sulphocyanate, 8 but 

 iodic acid is an exceedingly unstable compound, and the latter statement is 

 questionable. 



Sulphocyanate is often absent in human saliva. Some authors state that 

 it is found in dog's saliva, others that it is not ; the explanation may be that 

 its presence in dog's saliva is also not constant. It is said to be absent in the 

 saliva of the horse, ox, sheep, goat, and pig. 9 Leared 10 found that sulpho- 



1 See Maly, Hermann's "Handbueh," Bd. v. (2), S. 8. 



2 The older analysts were accustomed to proportion the bases and acids, on the 

 supposition that as much as possible of the so-called strongest acid was combined with the 

 strongest base. We now know that the acids and bases are distributed according to definite 

 laws, and no longer speak of so much chloride, for example, as existing in a complex 

 mixture, but state separately so much sodium and so much chlorine, etc. 



3 " Biologie," 1814, Bd. iv. S. 330. 



4 "Die Verdauung nach Versuchen," Bd. i. S. 8. 



5 See Maly, Hermann's "Handbueh," Bd. v. (2), S. 10, 14. 



6 Gscheidlen, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden. 1874, Bd. iv. S. 91. 



7 Bottger, ibid., 1872, Bd. ii. S. 204. 



8 Solera, ibid., 1877, Bd. vii. S. 256 ; 1878, Bd. viii. S. 235. 



9 Ellenberger and Hofmeister, " Vergleich. Phys. d. Haustiere," Berlin, 1890, S. 

 495. 



10 Proc. Roy. Soc. London, 1870, vol. xviii. p. 16. 



