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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
1 umerous 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, Nylen, 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, HgCl2 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, Pfluger’s Arch., 60.
2
See Hammarsten, Maly’s Jahresber., 1; Chittenden and Griswold, Amer. Chem.
Journ., 3; Langley, Journal of Physiol., 3; Nylen, 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; Kubel, Pfluger’s Arch., 56.
3
See O. Nasse, Pfluger’s Arch., 11, and Chittenden and Painter, Yale College
Studies, 1, 1885, 52; Kubel, Pfluger’s Arch., 76; Patten and Stiles, Amer. Journ. of
Physiol., 17.
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