456 DIGESTION. 



Ptyalin, or salivary diastase, is the amylolytic enzyme of the saliva. 

 This enzyme is found in human saliva, 1 but not in that of all animals, 

 especially not in the typical carnivora. It occurs not only in adults, 

 but also in new-born infants. In opposition to ZWEIFEL'S views, BER- 

 GER 2 claims that it is present not only in the parotid gland of children, 

 but also in the mucin glands. 



According to H. GOLDSCHMIDT s the saliva (parotid saliva) of the horse does 

 not contain ptyalin, but a zymogen of the same, while in other animals and man 

 the ptyalin is formed from the zymogen during secretion. In horses the zymogen 

 is transformed into ptyalin during mastication, and bacteria seem to give the 

 impulse to this change. During precipitation with alcohol the zymogen is changed 

 into ptyalin. 



Ptyalin has not been isolated in a pure form up to the present time. 

 It can be obtained purest by COHNHEIM'S 4 method, which consists in 

 carrying the enzyme down mechanically with a calcium-phosphate 

 precipitate, and washing the precipitate with water, which dissolves the 

 ptyalin, and from which it can be obtained by precipitating with alcohol. 

 For the study or demonstration of the action of ptyalin one employs a 

 watery or glycerin extract of the salivary glands, or simply the saliva 

 itself. 



Ptyalin, like other enzymes, is characterized by its action. This 

 consists in converting starch into dextrins and sugar. Our knowledge 

 as to the process going on here is just as uncertain as our knowledge 

 on the formation of sugar from starch (see page 229). The nature of 

 the sugar thus produced is known with certainty. For a long time it 

 was considered that glucose was the sugar formed from starch and 

 glycogen, but SEEGEN and O. NASSE have shown that this is not true. 

 MUCULTJS and v. MERING have shown that the sugar formed by the 

 action of saliva, amylopsin, and diastase upon starch and glycogen is 

 for the most part maltose. This has been substantiated by BROWN 

 and HERON. E. KULZ and J. VoGEL 5 have also demonstrated that 

 in the saccharification of starch and glycogen, isomaltose, maltose, and 

 some glucose are formed, the varying quantities depending upon the 

 amount of ferment and the length of its action. The formation of 



1 In regard to the variation in the quantity of ptyalin in human saliva see Hof- 

 bauer, Centralbl. f . Physiol., 10, and Chittenden and Richards, Amer. Journ. of Physiol., 

 1; Schiile, Maly's Jahresber., 29; Tezner, 1. c. 



2 Zweifel, Untersuchungen iiber den Verdauungsapparat der Neugeborenen (Berlin, 

 1874); Berger, see Maly's Jahresber., 30, 399. 



8 Zeitschr. f . physiol. Chem., 10. 



4 Virchow's Arch., 28. 



6 Seegen, Centralbl. f . d. med. Wissensch., 1876, and Pfliiger's Arch., 19; Nasse, 

 ibid., 14; Musculus and v. Mering, Zeitschr. f. physiol. Chem., 2; Brown and Heron, 

 Liebig's Annal., 199 and 204; Kiilz and Vogel, Zeitschr. f. Biologic, 31. 



