the J erusalem Artichoke ( Helianthus tuber os ns), 235 
frequently, and were tested carefully at intervals to see whether 
any difference of reducing power between the two dialysates 
could be detected as time went on. After three days both the 
dialysates were quite free from sugar, and during this period 
there was never any difference of reducing power to be 
observed. Had any ferment been present in the extract, the 
dialysate of A should have given evidence of its activity by an 
increased reducing power, but of this, as I have said, there was 
no indication. The sugar originally present in the extract 
was equally present in both dialysers, and it gradually dialysed 
out at the same rate in both. When this quantity had dis- 
appeared, there remained nothing in A that would reduce 
Fehling’s fluid, as there would had ferment been present. 
Both dialysers at the end of the experiment contained nearly 
as much inulin as at first, only a little having dialysed out 
during the experiment. Hence no ferment is present in the 
developing tubers. 
There remains for consideration the condition in which the 
antecedent of the ferment exists in the tubers till the onset of 
germination. From analogy with other ferments, both animal 
and vegetable, it appears probable that it is present in the 
form of a zymogen. In many cases this can be proved to be 
the antecedent form of ferment, as e.g. in the gastric and 
pancreatic glands in the animal body. An extract of these 
glands, taken while they are quite fresh, is found to possess no 
digestive powers, but to become active when warmed with 
a weak acid. A gland that has been kept warm for some 
hours before the extract is made is found to contain large 
quantities of the ferment. My first experiments on this point 
were made with very small tubers, and were not conclusive. 
Later in the year I was able to use tubers that had attained 
their full size, and with these I was more successful. 
Some full-grown artichokes were procured ; half of them 
were at once extracted with glycerine, as in the other cases 
described. The remainder were sliced each into about four 
pieces, and were put into a beaker over a bath at 35 0 C, and 
kept there for twenty-four hours, after which they were minced, 
s 
