90 Green. — On Vegetable Ferments . 
gradually converts it into sugar. The stages of the decom- 
position appear to be as complex as those noted in the 
hydrolysis of starch, intermediate bodies with characteristic 
reactions being present in the mixture. This transformation 
has been found to be due to a special enzyme, to which the 
name inulase may be given. It is a different body from 
diastase, for it has no action upon starch-paste. Inulase is 
present in the tuber in very small amount, and probably only 
occurs at any moment in the cells in which the hydrolysis of 
the inulin is actually taking place. Unlike the diastase of 
secretion it gives no histological evidence of its formation. 
Inulase is very sensitive to contact with acid or alkalis ; 
not only is its activity impaired by the presence of more 
than a trace of either in the fluid in which it is working, but 
exposure to -2 per cent, of HC 1 or 1*5 per cent. Na 2 C 0 3 
destroys it altogether. The destruction is more rapid at a 
moderately high temperature (40° C.) than at a lower one 
(10-15° C.). A trace of HC 1 , not more than -005 per cent, is 
rather advantageous than not, but so slight is this acidity 
that it may be said to work best in a neutral medium. Its 
optimum temperature is 40° C., and like other enzymes it is 
destroyed by boiling. 
Invertase. Another enzyme belonging to the first group is 
the body known as invertase , which is so named from its power 
of inverting cane-sugar, or hydrolysing it into dextrose and 
laevulose. Before cane-sugar can undergo alcoholic fermenta- 
tion this preliminary change must be effected, and the yeast 
itself which brings about the former decomposition also 
causes the hydrolysis, a fact ascertained by Dubrunfaut in 
1847. Hansen 1 has shown that invertase is present in 
several other micro-organisms ; Brown and Heron 2 found it to 
be present in the cold-water extract of malt ; Kossmann 3 
detected it in the buds and leaves of young trees, and Van 
Tieghem 4 in the pollen-grains of certain plants. Bechamp 5 
1 Medelelser, 1888, 2. 143. 2 Trans. Chem. Soc. 35, 1879, 609. 
3 Comptes rendus, 81, 406. 4 Bull. Soc. Bot. de France, t. 33, 1886. 
5 Mem. Acad. Sci. 28, 347. 
