regulating Metabolism . 5 1 3 
mixed with 4 emulsin Dogwood, the only English ally of Aucuba Japonica , 
does not blacken. 
The leaves of the well-known shrub Garrya elliptica,\hz male of which 
is grown on account of its decorative green catkins, change to an ugly grey 
colour in chloroform. The colourless extract obtained on boiling the leaves 
in water assumes a beautiful blue colour when digested with 4 emulsin \ 
We shall endeavour to extract the / 3 -glucoside which is indicated by this 
behaviour. 
Two other species of Garrya , G. macrophylla and G. Thureti , that we 
have tested behave similarly, although the latter gives but a weak effect. 
[Since this account was written, Herissey and Lebas have recorded the 
isolation of aucubin from these two species and also from G. elliptica .*] 
Aucubin has also been separated from several species of Plantago 
(Bourdier 2 ). 
It is well known that the seed-pods of many leguminous plants ulti- 
mately become black. Apparently, in most cases, the effect cannot be 
much hastened by means of chloroform — as a rule, the effect can only be 
produced 48-24 hours before the seed is ripe ; it would seem that either 
the enzyme or the substance which affords the black product comes into 
existence only at a late stage of growth. In the case of the ordinary Broad- 
bean, however, the pod can be caused to blacken at any time by exposure 
to chloroform. It is well known to botanists that the leaves of parasitic 
plants generally blacken with extreme readiness. We have found that the 
leaves of Drosera become intensely black when placed in toluene vapour. 
The last case to which we will refer is that of Mangel-wurzel. It is 
well known that when the root is pulped it changes colour ; if exposed in 
chloroform it soon blackens but the blackening is at first local. The 
blackening is shown also by sugar-beet but far less intensely. If a slice 
of the root, cut horizontally, be taken, the blackening takes the form of 
more or less circular rings of black dots ; in slices cut vertically, the whole 
vascular system is seen outlined in black. Gradually the colour spreads to 
the soft tissue outside the vascular system — whether because of the diffusion 
of the colouring matter or because the action actually extends into this 
region, we cannot say at present. We are inclined to think that in this case 
the localization of the colour in the vascular system is due rather to the 
localization of an enzyme than to that of a colouring material. We intend, 
if possible, to study these and other cases of melanism induced by anaes- 
thetics during the coming season, in the hope of deciding an issue that has 
already received attention at the hands of various observers several of 
whom have correlated the change with that occurring in cases of alkap- 
tonuria in the human subject. 
It would seem probable that in the case of many fruits the final 
1 loc. cit., 7 me s^rie, t. ii, 1910, p. 490. 2 Journ. Pharm. Chim., t. xxvi, 1907, p. 254. 
