346 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



cyanate was present in the blood and urine as well as in the saliva. 

 Gscheidlen l 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 ) 2 

 (cyanic acid) (ammonium (urea) 



cyauate) 



Sulphur compounds CKSH ; CKS.NH 4 ; CS.(NH 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, 1'46 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 0'5-0'S vols. of oxygen, O'9-l'O vols. 

 of nitrogen, and 64*73-85 '13 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 Firchow's Archiv, 1877, Bd. Ixix. S. 354. 



3 Fenwick, "The Saliva as a Test for Functional Disorders of the Liver," London, 1889. 



4 Schonbein, Journ. f. prakt. Chem., Leipzig, Bd. Ixxxvi. S. 151 ; Schaer, Ztschr.f. BioL, 

 Mlinchen, Bd. vi. S. 467 ; Griess, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. ii. S. 624. 



5 Maly, Hermann's "Handbuch," Bd. v. (2), S. 8. See also W. Sticker, Mimchen. 

 med. Wchnschr., 1896, Bd. xliii. Nos. 42-43. 



6 Ztschr. f. BioL, Mimchen, 1887, Bd. xxiii. S. 321. 



7 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 686. 



