PTYALIN. 431 



Sulphocyanides, which, although not constant, occur in the saliva of 

 man and certain animals, may be easily detected by acidifying the saliva 

 with hydrochloric acid and treating with a very dilute solution of ferric 

 chloride. As control, especially in the presence of very small quantities, 

 it is best to compare the test with another test-tube containing an equal 

 amount of acidulated water and ferric chloride. Other methods have 

 been suggested by GSCHEIDLEN, SOLERA, and GANASSINI. The quantita- 

 tive estimation can be done according to MUNK'S l method. 



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

 This enzyme is found in human saliva, 2 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 3 claims that it is present not only in the parotid gland of children, 

 but also in the mucin glands. 



According to H. GOLDSCHMIDT 4 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 5 method, which consists 

 in carrying the enzyme down mechanically with a calc'um-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 dextr fc ins 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 223) . The nature of the sugar 

 thus produced is known with certainty. For a" long time it was con- 

 sidered that dextrose was the sugar formed from starch and glycogen, 

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

 and v. MERING have shown that the sugar formed by the action of saliva, 



1 Gscheidlen, Maly's Jahresber., 4; Solera, see ibid., 1 and 8; Munk, Virchow's 

 Arch., 69; Ganassini, Biochem. Centralbl., 2, p. 361 



2 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. 



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

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



4 Zeitschr. f . physiol. Chem., 10. 



5 Virchow's Arch., 28. 



