

FUNCTIONS OF SALIVA. 219 



[Brown and Heron suggest that the final result of the transformation may be re- 

 presented by the equation 



10(C 12 H 20 O 10 ) + 8H 2 - 8(C 12 H 22 O n ) + 2(C 12 H 20 O 10 ) 



Soluble starch. Water. Maltose. Achroodextrin. 



The ferment slowly changes maltose into grape-sugar or dextrose. This result 

 may be brought about much more rapidly by boiling maltose with dilute sulphuric 

 or hydrochloric acid.] Achroodextrin ultimately passes into maltose, and this 

 again into dextrose ; the other form of dextrin does not seem to undergo this change 

 (Seegen's Dystropodextrin). For the further changes that maltose undergoes in 

 the intestine, see 183, II. 2. 



[The formula of starch is usually expressed as C 6 H 10 O 5 , but the researches already men- 

 tioned, and those of Brown and Heron, make it probable that it is more complex, which we 

 may provisionally represent by 7i(C 12 H 20 O 10 ). According to Musculus and Meyer, erythrodextrin 

 is a mixture of dextrin and soluble starch.] 



Preparation of Ptyalin. (1) Like all other hydrolytic ferments, it is carried down with any 

 copious precipitate that is produced in the fluid which contains it, and it can be isolated from 

 the precipitate. The saliva is acidulated with phosphoric acid, lime-water is added until the 

 reaction becomes alkaline, when a precipitate of the basic calcium phosphate occurs, which 

 carries the ptyalin along with it. This precipitate is collected on a filter, washed with water, 

 which dissolves the ptyalin, and from its watery solution it is precipitated by alcohol as a white 

 powder. It is redissolved in water and reprecipitated, and is obtained pure (Cohnheim). 



(2) Glycerine or v. Wittich's Method. The salivary glands [rat] are chopped up, placed in 

 absolute alcohol for twenty-four hours, taken out and dried, and afterwards placed in glycerine 

 for several days, which extracts the ptyalin. It is precipitated by alcohol from the glycerine 

 extract. 



(3) William Roberts recommends the following solutions for extracting fierments from organs 

 which contain them : (1) A 3 to 4 per cent, solution of a mixture of 2 parts of boracic acid and 1 

 part borax. (2) Water, with 12 to 15 per cent, of alcohol. (3) 1 part chloroform to 200 of water. 



Diastatic Action of Saliva. (a) The diastatic or sugar-forming action is known by (1) 

 The disappearance of the starch. When a small quantity of starch is boiled with several 

 hundred times its volume of water, starch-mucilage is obtained, which strikes a blue colour 

 with iodine. If to a small quantity of this starch a sufficient amount of saliva be added, and 

 the mixture kept for some time at the temperature of the body, the blue colour disappears. (2) 

 The presence of sugar is proved directly by using the tests for sugar ( 149). 



(b) The action takes place more slowly in the cold than at the temperature of the body its 

 action is enfeebled at 55 C, and destroyed at 75 C. (Paschutin). The most favourable 

 temperature is 35 to 39 C. 



(c) The ptyalin itself does not seem to be changed during its action, but ptyalin which has 

 been used for one experiment is less active when used the second time (Paschutin). 



Ptyalin differs from diastase the ferment in germinating grains in so far that the latter 

 first begins to act at +66 C. Ptyalin decomposes salicin into saligenin and grape-sugar 

 (Frerichs and Stddler). 



(d) Saliva acts best in an exactly neutral medium, but it also acts in an alkaline and even in a 

 slightly acid fluid; strong acidity prevents its action. The ptyalin is only active in the stomach 

 when the acidity is due to organic acids (lactic or butyric), and not when free hydrochloric acid 

 is present (van de Velde). In both cases, however, dextrin is formed. Ptyalin is destroyed by 

 hydrochloric acid or digestion by pepsin (Chittenden and Griswold, Langley). Even butyric 

 and lactic acids formed from grape-sugar in the stomach may prevent its action ; but if the 

 acidity be neutralised, the action is resumed (01. Bernard). 



(e) The addition of common salt, ammonium chloride, or sodium sulphate (4 per cent, solu- 

 tion), increases the activity of the ptyalin, and C0 2 , acetate of quinine, strychnia, morphia, 

 curara, 0*025 per cent, sulphuric acid, have the same effect. 



(/) Much alcohol and caustic potash destroy the ptyalin ; long exposure to the air weakens 

 its action, sodium carbonate and magnesium sulphate delay the action (Pfeiffer). Salicylic 

 acid and much atropin arrest the formation of sugar. 



(g) Ptyalin acts very feebly and very gradually upon raw starch, only after 2 to 3 hours 

 (Schiff) ; while upon boiled starch it acts rapidly. [Hence the necessity for boiling thoroughly 

 all starchy foods.] 



(h) The various kinds of starch are changed more or less rapidly according to the amount of 

 cellulose which they contain.; raw potato starch after 2 to 3 hours, raw maize starch after 2 to 

 3 minutes (Hammarsten) ; wheat starch more quickly than that of rice. When the starches 

 are powdered and boiled, they are changed with equal rapidity. 



. (i) A mixture of the saliva from all the glands is more active than the saliva from any single 

 gland (Jalcubowitsch), while mucin is inactive. 



