THE SALIVA. 125 



xanthoproteic reaction, the biuret reaction, and Millon's reaction. 

 It contains also a small amount of sulphur. On boiling with dilute 

 mineral acids mucin is decomposed into a substance which resembles 

 acid albumin, and into a carbohydrate-like body which reduces 

 Fehling's solution. This has been shown to be a glucosamin. 

 According to Muller, it is present to the extent of 23.5 per cent. 



Within the cells mucin exists as so-called mudnogen, which prob- 

 ably represents a compound of mucin with an additional albuminous 

 substance. 



Sulphocyanides. Traces of sodium sulphocyanide are in man 

 usually found in every specimen of normal saliva. It is secreted 

 by all the salivary glands, but in largest amount by the parotids. 

 In other animals its presence is not so constant, and in some indeed 

 it is not found. In man also it is at times absent. 



To demonstrate the presence of sulphocyanides, it usually suffices 

 to treat a few cubic centimeters of saliva, which have been slightly 

 acidified with hydrochloric acid, with a few drops of a very dilute 

 solution of perchloride of iron, when a red color will be seen to 

 develop. If no result is obtained in this manner, a larger quantity, 

 such as 100 c.c., is evaporated to a small volume and again tested as 

 described. 



Nitrites. Small amounts of nitrites may also at times be 

 observed, and are no doubt derived from the nitrates ingested. To 

 test for these, about 10 c.c. of saliva are treated with a few drops 

 of Ilasvay's reagent, and heated to a temperature of 80 C., when 

 in the presence of nitrites a red color develops. 



Ilasvay's reagent is prepared as follows : 0.5 gramme of sulph- 

 anilic acid in 150 c.c. of dilute acetic acid is treated with 0.1 

 gramme of naphtylarnin dissolved in 20 c.c. of boiling water. After 

 standing for some time the supernatant fluid is poured oif, and the 

 sediment dissolved in 150 c.c. of dilute acetic acid. The solution 

 is kept in a sealed bottle. 



Extractives. Of extractives, normal saliva contains a small 

 amount of urea, and traces of cholesterin, lecithin, and leucin. In 

 gouty conditions uric acid has been found ; sugar, the biliary pig- 

 ments, and biliary acids are not eliminated through the saliva. 



Mineral Constituents. The mineral constituents of saliva con- 

 sist to the extent of 90 to 92 per cent, of soluble salts, among which 

 the chlorides greatly predominate, and of about 6 per cent, of salts, 

 which are principally represented by the carbonates and phosphates 

 of calcium and magnesium, which are held in solution by the free 

 carbonic acid of the saliva. In addition, a trace of iron is found. 

 Following the administration of bromides and iodides a notable 

 elimination of these salts occurs through this channel. 



Gases. Of gases, which are present in a state of solution, we 

 find about 20 c.c. for every 100 grammes of saliva. Of these, 19 

 c.c. are represented by carbon dioxide, while oxygen and nitrogen 

 together amount to only 1 c.c. 



