328 CHEMISTRY OF THE DIGESTIVE PROCESSES. 
other hand, the optimum temperature for malt diastase lies at 50° to 
56° C. ; 1 the activity does not greatly diminish until 60° C. is passed, and 
then rapidly decreases and disappears, the ferment being destroyed by a 
temperature of 80° C. Malt diastase is also much more sensitive to the 
presence of salicylic acid than is ptyalin, being stopped by the presence 
of O'Oo per cent., while ptyalin is first affected by 01 per cent., and not 
completely stopped until a strength of 1 per cent, is reached.' 2 
There is unfortunately no such certainty as to the identity or non- 
identity of ptyalin and amylopsin (the diastatic ferment of the pancreas), 
which is also called ptyalin by some authors. 3 By others, the two 
enzymes are accounted different, because (a) the pancreatic action is more 
intense and complete, and (b) there are certain differences in the 
products formed by the action of the two enzymes. 4 It is, however, 
questionable whether these effects may not be entirely produced by 
differences in concentration in the two cases of one and the same 
ferment. In their behaviour to change of temperature and reaction the 
two enzymes are identical ; the rate of conversion of starch into other 
substances depends on the concentration of the enzymes in the solution ; 
and with regard to differences in the products formed, it is not denied 
that in prolonged salivary digestion a small quantity of dextrose is 
formed, it is only claimed that larger quantities of dextrose are 
formed in a shorter time 5 by the action of the diastatic enzyme of the 
pancreas ; tins again is a difference in degree and not in kind, and may 
well be due to a difference in concentration of enzyme. 
Cohnheim 6 obtained ptyalin in a purer form, that is, more free from 
admixed proteids, by a method closely resembling that of Briicke for 
pepsin, and consisting essentially in producing a precipitate of tricalcic 
phosphate in the saliva by the addition of phosphoric acid followed by 
milk of lime ; this precipitates mechanically ptyalin and proteid, the 
ptyalin dissolves more easily than the proteid on afterwards washing 
the precipitate with distilled water, and may in this way be separated. 
The solution so obtained was actively diastatic, but yet gave none of 
the usual proteid reactions, was not coagulated on boiling, gave no 
react inns with nitric acid, mercuric chloride, tannin, iodine, or acetic acid 
and potassium ferrocyanide. The ptyalin precipitated from it was not 
a pure substance, but contained chlorides and phosphates of sodium and 
calcium. 
Excess of alcohol caused a flocky precipitate of phosphates, and an 
amorphous granular substance coloured yellow by iodine. Dried at a low 
temperature, this precipitate furnished a white powder, only slightly 
soluble in water, which retained its diastatic action for months. 
A very active material may also be obtained by v. Wittich's method 
1 Chittenden and Martin, Stitd. Lab. Physiol. .Cliem., New Haven, 1885, vol. i. p. 117 ; 
abstract in Jahresb. it. d. Fortschr. J. Thier-Chem., Wiesbaden, 1885, Bd. xv. S. 263; 
Lintner and Eckhard, Jov.ru. f. praM. Chem., Leipzig, 1891, N. F., Bd. xli. S. 91 ; Stutzer 
and Isbert, Ztschr. f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 72. 
2 Jul. Midler, Journ.f. prakt. Chem., Leipzig, 1875, N. F., Bd. x. S. 45. 
3 Xeumeister, "Lehrbuch der physiol. Chem.," Jena, 1893, Th. 1, S. 147. 
4 See Sheridan Lea, " Chemical Basis of the Animal Body," London, 1892, p. 57. 
5 Lea, however, found no dextrose, but only maltose, in his experiments quoted on p. 394. 
See also Brown and Heron, Proc. Boy. Soc. London, 1880, No. 204, p. 393 ; Musculus and 
Gruber, Ztschr. f. physiol. Cliem., Strassburg, 1878-9, Bd. ii. S. 177 : Mnsculus and v. 
Mering. ibid., S. 403 ;' v. Mering, ibid., 1881, Bd. v. S. 185. 
6 Virchow's Archiv, 1863, Bd. xxviii. S. 241. Compare Sundberg's statement as to 
similar precipitation of pepsin by alcohol and not by tannic acid, p. 316. 
