346 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 
cyanate was present in the blood and urine as Avell as in the saliva. 
Gscheidlen * and Munk 2 have also found it in urine. 
An exalted importance has been given to the sulphocyanate in saliva, 
from its supposed origin from proteid, and from its assumed value as an 
indicator of the rate of proteid metabolism. Sulphocyanic acid has a 
similar constitution to cyanic acid, an atom of sulphur merely replacing an 
atom of oxygen, and the ammonium salt of sulphocyanic acid undergoes a 
similar decomposition to that of cyanic acid, yielding sulpho-urea instead 
of urea, thus : — 
Oxygen compounds— CK OH ; CN.O.NH 4 ; CO.(NH 2 ), 
(cyanic acid) (ammonium (urea) 
cyanate) 
Sulphur compounds— CKSH ; CN.S.NH, ■ CS.(jS t H 2 ) 2 
(sulphocyanic (ammonium (sulpho-urea) 
acid) sulphocyanate) 
From this relationship, from the presence of sulphur in its molecule, and 
from its presence in the urine, and in traces in the blood, it is probable that 
the sulphocyanate of the saliva is a product of proteid metabolism. Fenwick 3 
has investigated the variation in the sulphocyanate of the saliva, especially in 
relation to the variations in the nutrition of the body under pathological 
conditions. He states that the amount of sulphocyanate bears a relationship 
to the amount of sulphur (as taurocholates) in the bile, and that when the 
bile is diverted from the alimentary canal the sulphocyanate of the saliva 
disappears. That it would be dangerous to take the amount of sulphocyanate 
as any gauge of the amount of proteid metabolism, is shown by its complete 
absence in many species of animals, and in many individuals where it is 
normally present in a species ; this does not make any the less probable 
the statement that in those individuals in which sulphocyanate is present its 
quantity should vary with the activity of proteid metabolism. 
Saliva also contains traces of nitrites, 4 which may be demonstrated by 
diluting saliva with five times its volume of water, making acid with sul- 
phuric acid and adding a solution of metadiamido-benzol, when an intense 
yellow colour is produced. In this way Griess estimated colorimetrically 
the amount of nitrite in saliva at 1-10 mgrms. per litre. Minute traces of 
ammonia may also be shown to be present in saliva by the addition of Nessler's 
reagent. 5 
Gases of the saliva. — The saliva holds considerable volumes of gas in 
solution or in chemical combination. In human parotid saliva, Kiilz 6 found 
in 100 vols, of saliva, of oxygen, 146 vols.; of nitrogen, 2 - 8 vols.; and of 
carbon-dioxide 66 '7 vols., of which latter 62 vols, were in chemical 
combination. In submaxillary saliva of the dog, obtained by stimulating 
the chorda tympani, Pfliiger 7 found - 5-0 - 8 vols, of oxygen, 0*9-1 - vols, 
of nitrogen, and 64'73-85T3 vols, of carbon-dioxide, most of the latter 
being chemically combined. These figures are interesting, both because of the 
large amount of carbon-dioxide present, and the fact that the oxygen exceeds 
the amount dissolved by blood plasma. 
1 Arch. f. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 401. 
2 Virchmo's Archiv, 1877, Bd. lxix. S. 354. 
3 Fenwick, "The Saliva as a Test for Functional Disorders of the Liver," London, 1889. 
4 Schonbein, Journ. f. prakt. Ohem., Leipzig, Bd. lxxxvi. S. 151 ; Schaer, Ztschr.f. Biol., 
Miinchen, Bd. vi. S. 467 ; Griess, Bcr. d. deutsch. chcm. Gesellsch., Berlin, Bd. ii. S. 624. 
5 Maly, Hermann's "Handbuch," Bd. v. (2), S. 8. See also W. Sticker, Miinchen. 
vied. JVchnschr., 1896, Bd. xliii. Nos. 42-43. 
6 Ztschr.f. Biol, Miinchen, 1887, Bd. xxiii. S. 321. 
7 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 686. 
