( 197 ) 
I soon obtained better results: bark from the stem was placed in 
96% alcohol immediately after the pealing of the branches; the 
alcohol was allowed to evaporate slowly in the air and after some 
days the liquid which was only feebly alcoholic, was filtered. On 
the addition of salicin 9 % was hydrolysed after 24 hours, after 
48 hours 17%, after 96 hours again only 9 %,' measured by the 
glucose formed. 
Young shoots were also ground in a mortar and pressed through 
fine plancton gauze, the juice was treated with an excess of 96% 
alcohol; a white precipitate was thus formed, which was filtered off, 
washed with alcohol and finally dissolved in water. The colourless 
slightly opalescent liquid, thus obtained, did not reduce Fehling’s 
solution, did not contain saligenol or catechol and hydrolysed on the 
addition of salicin after 24 hours 8% > after 48 hours at 40 28 /„, 
after 72 hours 46%. The extent of the hydrolysis was measured by 
estimating the glucose formed; in the ethereal extract saligenol could 
be demonstrated 1 * ). From the young shoots a mixture of enzymes had 
thus been obtained, among which was an enzyme which splits salicin 
into glucose and saligenol ’). I obtained the same enzyme from Populus 
canadensis Mchs. 
The salicase is not identical with emulsin, nor with amygdalase, 
for it does not bring about the decomposition of amygdalin. 
The above mentioned experiment with the weakly alcoholic extract 
of the bark, pointed to a reversible action of the enzyme, as did 
also some other experiments. For when 1 dissolved 200 mgs. of 
glucose and 100 mgs. of saligenol in 2 cc. of water and added 
salicase (with thymol as antiseptic), the reducing power was diminished 
by 5% after 2 days at 40°, which diminution might be explained 
by the possible formation of salicin 3 ). I had not, however, sufficient 
material to make this out with certainty. 
The discovery of this salicase induced me to investigate once more 
the occurrence of saligenol in Salix purpurea, as formerly I had only 
been able to find minute traces. For this purpose I compared in the 
l ) Recognized by allowing the sublimate of the ethereal extract to crystallize 
from aqueous solution, and by the reactions with cupric acetate and with ferric 
chloride. 
•> When 1 had already completed my investigation, my attention was drawn to 
a paper by W. Sigmund (Sitz. ber. Akad. d. Wiss. Wien. CXV1I. Bd IX 1909) who 
obtained from other species of Salix and of Populus an enzyme, called by him 
salicase, which hydrolyses salicin, and from Calluna vulgaris and Vaccmium myr- 
tillus an arbutase, which hydrolyses arbutin. 
s ) After boiling with dilute hydrochloric acid the reducing power was again as 
great as before* 
Proceedings Royal Acad. Amsterdam, Vol, XII. 
14 
