2l8 PHYSIOLOGICAL ACTION OF SALIVA. 



According to Schunbein, the saliva contains traces of nitrites, (detected by adding dilute 

 sulphuric acid and diamido-benzol to dilute saliva), which give a yellow colour (Gries). There 

 are also traces of ammonia (Briicke). 



Abnormal Constituents. In diabetes mellitus, lactic acid, derived from a further decomposi- 

 tion of grape-sugar, is found. It dissolves the lime in the teeth, giving rise to diabetic dental 

 caries. Frerichs found leucin, and Vulpian increase of albumin in albuminuria. Of foreign 

 substances taken into the body, the following appear in the saliva : Mercury, potassium, 

 iodine, and bromine. 



Saliva of New-Born Children. In new-born children, the parotid alone contains 

 ptyalin. The diastatic ferment seems to be developed in the sub-maxillary gland 

 and pancreas, at the earliest after two months. Hence, it is not advisable to give 

 starchy food to infants. No ptyalin has been found in the saliva of infants suffer- 

 ing from thrush (Oidium albicans Zweifel). The diastatic action of saliva is not 

 absolutely necessary for the suckling, feeding as it does upon milk. The mouth 

 during the first two months is not moist, but at a later period saliva is copiously 

 secreted (Korowin) ; after the first six months, the salivary glands increase con- 

 siderably. The eruption of the teeth owing to the irritation of the mucous 

 membrane produces a copious secretion of saliva. 

 NL 148. PHYSIOLOGICAL ACTION OF SALIVA. I. Diastatic Action. The 

 /most important chemical action exerted by saliva in digestion is its diastatic or 

 amylolytic action (Leuchs, 1831), i.e., the transformation of starch into dextrin and 

 some form of sugar. This is due to the ptyalin a hydrolytic ferment or enzym 

 which, even when it is present in very minute quantity, causes starch to take up 

 water and become soluble, the ferment itself undergoing no essential change in the 

 process. [Ptyalin belongs to the group of unorganised ferments ( 250, 9). Like 

 all other ferments it acts only within a certain range of temperature, being most 

 active about 40 C. Its energy is permanently destroyed by boiling. Its acts best 

 in a slightly alkaline or neutral medium.] 



[Action on Starch. Starch-grains consist of granulose or starch enclosed by 

 coats of cellulose. Cellulose does not appear to be affected by saliva, so that saliva 

 acts but slowly on raw unboiled starch. If the starch be boiled, so as to swell up 

 the starch-grains, and rupture the cellulose envelopes, the amylolytic action takes 

 place rapidly. If starch-paste or starch-mucilage, made by boiling starch in water, 

 be acted upon by saliva, especially at the temperature of the body, the first physical 

 change observable is the liquefaction of the paste, the mixture becoming more fluid 

 and transparent. The change takes place in a few minutes. When the action is 

 continued, important chemical changes occur.] 



According to O'Sullivan, Musculus, and v. Mering, the diastatic ferment of saliva 

 (and of the pancreas), by acting upon starch or glycogen, forms dextrin and maltose 

 (both soluble in water). Several closely allied varieties of dextrin, distinguishable 

 by their colour-reactions, seem to be produced {Briicke). Ery thro dextrin is 

 formed first, it gives a red colour with iodine j then a reducing dextrin achroo- 

 dextrin, which gives no colour- reaction with iodine. The sugar formed by the 

 action of ptyalin upon starch is maltose (C 12 H 22 O n + H 2 0), which is distinguished 

 from grape-sugar (C 12 H 24 12 ) by containing one molecule less of water, which, how- 

 ever, it holds as a molecule of water of hydration. [Maltose also differs from grape- 

 sugar in its greater rotatory power on polarised light, the former = + 150, thejlatter 

 + 56, the ratio being '61 : 100 ; and in its smaller power of reducing cupric oxide. 

 Thus, between the original starch and the final product, maltose, several interme- 

 diate bodies are formed. The starch gives a blue with iodine, but after it has been 

 acted on for a time it gives a red or violet colour, indicating the presence of ery- 

 throdextrin, there being a simultaneous production of sugar ; but ultimately no 

 colour is obtained on adding iodine achroodextrin, which gives no colour with 

 iodine, maltose being formed. The presence of the maltose is easily determined 

 by testing with Fehling's solution.] 



