Studies on Enzyme Action. 321 
The two arrows are introduced to indicate the direction from which 
hydrolytic attack may be supposed to proceed: a molecule open to attack in 
such manner would, doubtless, be far less stable than one in which only a 
single contiguous oxygen centre serves to direct the attack. 
The hydrolysis of melibiose and of raffinose by emulsin lactase will be con- 
sidered in a later communication ; the hydrolysis of melibiose by acids and by 
melibiase will also be dealt with separately. 
Studies on Enzyme Action. XI.—The Enzymes of Emulsin. 
By H. E. Armstrone, F.R.S., E. F. Armstronec, D.Se., and E. Horton, B.Se. 
(Received and read April 2, 1908.) 
[International Catalogue of Scientific Literature. 
Authors’ title slip :—D. Q. 
Subject slips :— 
D 1850 Amygdalin, hydrolysis by emulsin to amygdonitrileglucoside. 
D 8014 Emulsin (almond)—presence in, of three enzymes. 
Q 1240 Amygdalase, presence of, in almond emulsin. 
D 8012 
Q 1230 
D 6300 Hydrogen cyanide (from amygdalin). 
D 6350 Glucose (from amygdalin)]. 
} Lactose, hydrolysis of, by glucolactase. 
Emulsin has frequently been the subject of discussion in this series of 
studies: thus the rate at which it hydrolyses milk-sugar was considered in 
No. If (vol. 73, pp. 507, 515) and its action contrasted with that of Kephir- 
lactase, which was shown to act more rapidly than emulsin. In No. III 
(vol. 73, p. 518) it was pointed out that whilst Kephir-lactase is controlled by 
galactose and scarcely at all by glucose, emulsin is controlled by glucose and 
only to a minor extent by galactose. These conclusions were confirmed by 
experiments with the methyl-glucosides and galactosides (p. 523). In No. V 
(vol. 74, p. 188) the question was discussed whether emulsin proper 
hydrolyses milk-sugar or whether, as Bourquelot and Hérissey have 
contended, emulsin contains a small proportion of lactase : against this assump- 
tion it was argued that the curve was not of the form to be expected if only 
a small quantity of lactase were present; that whereas Kephir-lactase was 
controlled by galactose alone, emulsin was most retarded by glucose and only 
toa slight extent by galactose, also that the curves for emulsin differed in 
