PTYALIN. 457 



glucose is claimed by TEBB, ROHMANN, and HAMBURGER 1 to be only a 

 product of the inversion of the maltose by the maltase. 



The action of ptyalin in various reactions has been the subject of 

 numerous investigations. 2 Natural alkaline saliva is very active, but 

 it is not so active as when made neutral. It may be still more active 

 under certain circumstances in faintly acid reaction, and according to 

 CHITTENDEN and SMITH it acts better when enough hydrochloric acid 

 is added to saturate the proteins present than when only neutralized. 

 When the acid-combined protein exceeds a certain amount, then the 

 diastatic action is diminished. The addition of alkali to the saliva 

 decreases its diastatic action; on neutralizing the alkali with acid or 

 carbon dioxide the retarding or preventive action of the alkali is arrested. 

 According to SCHIERBECK, carbon dioxide has an accelerating action in 

 neutral liquids, while EBSTEIN claims that it has, as a rule, a retarding 

 action. Organic as well as inorganic acids, when added in sufficient 

 quantity, may stop the diastatic action entirely. The degree of acidity 

 necessary in this case is not always the same for a certain acid, but is 

 dependent upon the quantity of ferment. The same degree of acidity 

 in the presence of large amounts of ferment has a weaker action than in 

 the presence of smaller quantities. Hydrochloric acid is of special 

 physiological interest in this regard, for it prevents the formation of 

 sugar even in very small amounts (0.03 p. m.). Hydrochloric acid has 

 not only the property of preventing the formation of sugar, but, as 

 shown by LANGLEY, NYLN, and others, may entirely destroy the 

 enzyme. This is important in regard to the physiological significance 

 of the saliva. 



Foreign substances, such as metallic salts, 3 have different effects. 

 Certain salts, even in small quantities, completely arrest the action; 

 for example, HgCk accomplishes this result completely in the presence 

 of only 0.05 p. m. Others have an accelerating action, and this seems 

 to apply to the salts of the saliva. According to GUYENOT the saliva 

 has a weaker action the more it is freed from salts by dialysis. On the 



1 Tebb, Journ. of Physiol., 15; Rohmann, Ber. d. deutsch. chem. Gesellsch., 27; 

 Hamburger, Pfliiger's Arch., 60. 



2 See Hammarsten, Maly's Jahresber., 1; Chittenden and Griswold, Amer. Chem. 

 Journ., 3; Langley, Journal of Physiol., 3; Nyle"n, Maly's Jahresber., 12, 241; Chit- 

 tenden and Ely, Amer. Chem. Journ., 4; Langley and Eves, Journal of Physiol., 4; 

 Chittenden and Smith, Yale College Studies, 1, 1885, 1; Schlesinger, Virchow's Arch., 

 125; Schierbeck, Skand. Arch. f. Physiol., 3; Ebstein and C. Schulze, Virchow's 

 Arch., 134; Klibel, Pfltiger's Arch., 56. 



3 See O. Nasse, Pfliiger's Arch., 11, and Chittenden and Painter, Yale College 

 Studies, 1, 1885, 52; Kiibel, Pfliiger's Arch., 76; Patten and Stiles, Amer. Journ. of 

 Physiol., 17. 



