ii EXTERNAL DIGESTIVE SECBETIONS 83 



Water ... ... . 



Solid substances ... . .V797 



Eiiithelia and mucin . . -2--2Q-2 



Ptyalin and globulin ... . 1 :',:iu 



Inorganic salts ....... 2 2o.~> 



Sulphocyanide of potassium .... 0041 



The same author found in 1000 parts of ash of human saliva : 



Potassium ... . . . . 457-3 



Sodium . . . 95-9 



Ferric oxide . . . 50 1 



Magnesium . . . .... 1/5 



Sulphuric acid . . . . . 63-8 



Phosphoric acid . . ... 188'.~> 



Chlorine ...... . 183'5 



Iii order to obtain and analyse separately the saliva of the 

 respective glands, the excretory ducts of Stensen and Wharton 

 can be syringed with special metal cannulae (Ordensteiu, Oehl, 

 Eckhard) in man, and on dogs artificial fistulae of the same canals 

 can be established. 



The parotid saliva of man is thin from absence of niucin, but 

 it becomes ropy and viscid if the secretion is scanty ; the reaction 

 is alkaline ; it is rich in ptyaliu even in the newborn ; contains 

 but little globulin. Constituents, 99 - 5 per cent water, 0'5 per 

 cent solids, of which 0'2 per cent are alkaline chlorides, - 2 per 

 cent carbonate of lime, and 015 per cent organic compounds, of 

 which 0'03 are sulphocyanide (Oehl). 



The submaxillary and sublingual saliva in man is more watery, 

 more alkaline, more viscid, because it contains mucin : it has a 

 weaker diastolic action, because it contains less ptyalin ; and the 

 amount of sulphocyanide is less (Oehl). 



Lastly, the submaxillary and sublingual saliva differs under 

 the microscope from parotid saliva, in containing many more 

 salivary corpuscles and shed mucous cells. 



Colinheim's method is the best for extracting a tolerably pure ptyalin 

 from saliva. () The saliva is strongly acidified with phosphoric acid (using 

 2 litres of mixed saliva) ; (ft) the filtrate i- then made alkaline with milk of 

 lime, which forms a precipitate of tri basic phosphate of lime and brings 

 down the ptyalin ; (c) the precipitate is collected on a filter and washed 

 with distilled water, which dissolves ptyalin ; (d) 5-6 volumes of alcohol are 

 added to the filtrate, when a flocculent precipitate is formed ; this is dried 

 /// vacua ; (e) this precipitate is redissolved in distilled water, filtered and 

 reprecipitated with absolute alcohol ; the precipitate is dried, and consists of 

 purified ptyalin. 



To show the presence of sulphocyanide of potassium in the saliva, add a 

 few drops of perchloride of iron, after acidifying with dilute hydrochloric 

 acid. The fluid turns more' or less blood-red, according to the amount of 

 sulphocyanide contained in the saliva (Oehl). 



Solera's reaction is based on the fact that the sulphocyanide separates 

 iodine from the iodic acid. On adding starch paste and then iodic acid to 

 the saliva, the iodine is liberated, and gives a blue colour witli starch. 



G 1 



