SPE CIFIC A CTION OF ENZ i 'MES. 3 2 7 
Specific action of enzymes.— The different enzymes are specific in 
their action; that is to say, each enzyme onhj acts on one cla 
material and acts on it in a determinate manner, producing certain 
specific Bubstances as the resull of thai action. The table on p. 326 is 
a classification of the digestive enzymes according to their specific action. 
Description of the digestive enzymes. — The digestive enzymes 
may be here must conveniently treated of according to their occurrence 
in the various digestive secretions, because of the description of the mode 
of their separation, where more than one is found in the same digestive 
fluid. Their action on the different classes of foodstuffs and the products 
formed thereby will be considered afterwards. 
Ptyalin.— in the saliva 1 if many animals, and especiallyin the herbivora, 
a diastatie enzyme is found, to winch, soon after the discovery that saliva 
possessed such an action, 3 the name ptyalin was applied. In fishes 
and in cetacea no salivary glands are present,'- and in some other 
animals the salivary secretion possesses no diastatie action ; for example, 
the saliva of the dog has no diastatie action, and the same statement is 
made for the typical carnivora in general. 3 In man, the secretion of both 
the parotid and submaxillary glands has a diastatie action. At birth the 
ferment is only found in the parotid : it makes its first appearance hi 
the submaxillary two months later. 1 In the horse the secretion leaves 
the parotid with the diastatie ferment still in the condition of a 
zymogen, from which the enzyme is set free by treatment with alcohol 
or by contact with unfiltered air. 5 
Ptyalin was first separated from saliva in an impure form by 
Mialhe, 6 by precipitating filtered saliva with excess of absolute alcohol. 
A scanty flocculent proteid precipitate is so obtained, which carries 
down the ptyalin mechanically. Mialhe showed that this precipitate, 
which was insoluble in strong alcohol, but partly soluble in water or 
weak alcohol, possessed when dissolved the diastatie power of the 
original saliva. From its supposed identity with the diastase of malt, 
he called it diastase animal ou salivaire, and used the term yityalin as a 
synonym. It is now known that ptyalin and malt diastase, though 
alike in their action upon starch, are not identical. This is shown best 
by the difference in the reaction of the two enzymes to changes in 
temperature. According to Eoberts, 7 saliva possesses a maximum 
action between the temperatures of 30° and 45° C, and, according to 
Kjeldahl, 8 the optimum temperature is 46° C, while the enzyme is rapidly 
destroyed by a temperature lying between G5 C and 70" C. 9 On the 
1 Leuclis, Arch.f. d. yes. Xaturl., Niirnberg, 1831 ; Schwann, Ann. d. Phys. u. ( 
Leipzig, 1836, Bd. xxxviii. S. 358. 
-According to Krukenberg ("Grundziige einer vergleich. Physiol, der Verdauung," 
1882, S. 67), in some fishes the secretion of the mucous glands of the mouth possesses a 
diastatie action; the same is true of the mucous secretion of the frog's mouth. 
3 Grutzner, Arch.f. d. ges. Physiol., Bonn, 1S76, Bd. xii. S. 285; Bunge, "Lehrbuch 
der physiol. Chem.," Leipzig, 1894, Ann. 3, S. 140; Neumeister, "Lehrbuch der 
physiol. Chem., etc.," Jena, 1893, Th. 1, S. 122. 
4 Zweifel, "Untersuch. ueber den Verdauungsapparat. der Xeugeborenen." Berlin, 
1874. See also Schiffer, Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1872, Bd. 
ii. S. 205 ; Korowin, ibid., 1873, Bd. iii. S. 158 ; Bayer, ibid., 1876, Bd. vi. S. 172. 
5 Goldschmidt, Ztschr. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 273. 
u Compt. rend. Acad. d. sc, Paris, 1845, tome xx. pp. 654, 14S3. 
7 " Digestion and Diet," London, 1891, p. 79. 
8 Abstract in Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1S79, Bd. ix. S. 381. 
9 Roberts, loc. cit. ; Kuhne states that saliva loses its activity at a temperature of 
60° C. ("Physiol. Chem.," S. 21). 
