328 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



other hand, the optimum temperature for malt diastase lies at 50 to 

 56 C. ; l 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 0-05 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 tlfe 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 ; this 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 Brlicke 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 

 reactions 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, Stud. Lab. Physiol. Chem., New Haven, 1885, vol. i. p. 117 ; 

 abstract in Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1885, Bd. xv. S. 263; 

 Lintner and Eckhard, Journ. f. prakt. Chem., Leipzig, 1891, N. F., Bd. xli. S. 91 ; Stutzer 

 and Isbert, Ztschr. f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 72. 



2 Jul. Miiller, Journ. f. prakt. Chem., Leipzig, 1875, N. F., Bd. x. S. 45. 



3 Neumeister, " 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. Roy. Soc. London, 1880, No. 204, p. 393 ; Musculus and 

 Gruber, Ztschr. f. physiol. Chem., Strassburg, 1878-9, Bd. ii. S. 177; Musculus 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. 



