324 Prof. Armstrong, Dr. Armstrong, and Mr. Horton. [Apr. 2, 
is full of pitfalls and difficulties: it was always obvious that the enzymes 
were mixtures, and the evidence constantly forced upon us that the products 
are mixtures has been in no sense a surprise, To carry the investigation to a 
successful issue, we have not only to overcome the difficulties incident on the 
preparation of considerable quantities of the enzymes in suitable condition, 
but also to devise special methods of separating, purifying and definitely 
characterising the products. 
Preparation of Hmulsin—Emulsin being an article of commerce, a dried 
solid preparation obtained from Merck, of Darmstadt, was made use of in the 
experiments referred to in the earlier communications of this series. This 
was always found to be active towards both amygdalin and milk-sugar. A 
similar preparation obtained from Kahlbaum in 1906 was almost worthless, 
being without action on milk-sugar even at 36° and acting only slowly on 
8-methylglucoside and salicin. We were led by the observations of these 
differences to prepare fresh emulsin from almonds, in the expectation that it 
would be much more active than a dried preparation ; this proved to be the case. 
The almonds—either the sweet or bitter variety may be used—were 
reduced to a pulp by passing them between rollers; the pulp was then pressed 
to remove as much as possible of the oil and afterwards macerated during 
about 24—48 hours with about two or three times its weight of water 
containing a little toluene. The most active preparations are obtained by 
extracting at a moderately low temperature, about 10°—20°. The cloudy 
liquid obtained on filtering the extract was mixed with two drops of acetic 
acid per 100 cc, to precipitate part of the albuminoids present; the 
relatively clear liquid obtained, after separating the precipitate by filtration, 
was then mixed by degrees with about an equal volume of alcohol. The 
precipitate thrown down by the alcohol was allowed to subside and then 
washed by decantation with alcohol ; finally, it was removed to a filter-paper. 
The adhering alcohol having been absorbed as far as possible by means of 
filter-paper, the moist solid was shaken up with distilled water containing 
toluene, the amount of water being varied according to the strength of the 
extract desired. After remaining in contact with the solid during 48 hours, 
at 37°, the solution was filtered and the residue again extracted with water. 
The extract thus obtained is a colourless, clear liquid, admirably suited for 
polarimetric work. 
Lactoclastic Power of “ Emulsin.”—In comparative experiments made with 
such a solution, at 15° and 36°, with milk-sugar and 8-methylglucoside, the 
glucoside underwent hydrolysis to a considerable extent at the lower 
temperature, whereas the milk-sugar was but slightly attacked; at the higher 
temperature, both were hydrolysed comparatively rapidly. 
