34 



starch into dextrin, maltose, and some dextrose. It is not able 

 to penetrate the g-ranule of unboiled starch, or does so very 

 slowly, differing- in this respect from the corresponding- enzyme 

 of the pancreas. It acts best at about the temperature 40° C. 

 Ptyalin ^s destroyed by acids— especially the mineral acids. 

 In the saliva of some animals, as the horse, the enzyme is not 

 present In the free state but as a zymogen from -which it read- 

 ily forms in mastication. [Novy] . 



To obtain mixed saliva. Che-w a small piece of paraf&n 

 or chewing gum, or inhale ether for a short time to stimulate 

 the flow of the secretion. Collect it in a graduate until you 

 have about 50 cc. Note that, in a short time, more or less of 

 a sediment occurs due to the deposition of epithelial cells, 

 debris of food, bacteria, etc. Numerous air bubbles are usually 

 present upon the surface. 



Filter. Is it translucent ? Is there any great amount of 

 viscidity ? What is its reaction to litmus paper ? The specific 

 gravity is 1002-1006. Test the specific gravity with an urin- 

 ometer. 



103. To a small portion add acetic acid., A precipitate 

 indicates mucin. Not soluble in excess. 



104. With another portion test for traces of proteids with 

 the xanthoproteic reaction and Millon's test. 



104 J^ . To a few drops of saliva in a porcelain evaporating- 

 dish add a few drops of dilute acidulated ferric chloride, — a 

 red coloration indicates the presence of sulphocyanide of potas- 

 sium, the color does not disappear on heating, nor on the 

 addition of an acid, but is discharged by mercuric chloride. 

 Meconic acid gives a similar color, but it is not discharged by 

 mercuric chloride. The sulphocyanide is present only in the 

 secretion from the parotid gland. 



105. Test for nitrites with a few drops of a starch solu- 

 tion acidified with a little dilute sulphuric acid and containing- 

 a small amount of potassium iodide. A nitrite immediately 

 gives a blue color. 



106. Test for chlorides by adding to the saliva a few 

 drops of nitric acid followed by a few drops of silver nitrate. 

 A white precipitate indicates the combination of the chloride 

 with the silver to form silver chloride. 



