1090 Irving. — The Effect of Chloroform 
in respiration, possibly from the wounding of the leaf. The rest of the two 
curves are almost identical. 
Each leaf weighed 2*3 grms. and both were brown at the conclusion of 
this experiment. 
It will now be interesting to compare the types of curve obtained in 
this section with those recorded in Section I. We find again the series 
from B to E following one another in the same order with increasing 
concentrations of the chloroform. We see, however, that a continuous 
exposure to the vapour is somewhat more effective than an initial dose of 
the same amount. Thus a curve which may be located as B-C would 
be given by an initial dose of 0*15 c.c. 
and by a continuous dose of 0-08 c.c. 
per litre ; a curve of type C-D by initial 
dose of 0*5 c.c. and continuous concen¬ 
tration of o-22 c.c. per litre. Roughly 
speaking, an initial dose of between 2 11 
and 3 n has the same effect as a con¬ 
tinuous dose of n per hour when the ex¬ 
periment takes place in an air-current of 
a litre per hour. 
It is clear that it is the initial stages 
of action of the vapour which are most 
significant, and that, when these changes are once set going, the final 
stages run their course much the same whether the vapour is still being 
applied or has been stopped. 
Some other effects of chloroform upon leaves. 
Moderate doses of chloroform bring about a destruction of chlorophyll 
and an exudation of sap in Barley leaves (cf. p. 1079). In Cherry Laurel 
there are two further symptoms easily observed, liberation of hydrogen 
cyanide from the cyanogenetic glucoside and the browning of the leaf. 
The browning would mask the chlorophyll even were it unchanged 
in the metabolic breakdown, but extraction tests with alcohol show that 
destruction of the chlorophyll goes on at the same time as browning, and 
no trace of green pigment can be extracted from a fully brown leaf. 
A few observations on the effect of temperature and of water-content 
on the rate of browning and of the breakdown of the cyanogenetic glucoside 
were made by using Guignard’s test-paper, 1 which turns from yellow to red 
in the presence of HCN. 
Leaves of Cherry Laurel treated with equal amounts of chloroform, in 
bottles, were kept at different temperatures, and the time taken for the 
1 Filter paper soaked in 1 % picric acid, dried, and then soaked in 10 % sodium carbonate. 
hours O 2 €> 8 10 12 K 16 IS 
Fig. 16. 
