Notes . 
37i 
destructive influence on certain enzymes that are excreted by various 
bacteria. 
From a consideration of these two facts it seems possible that light 
may be destructive to the ordinary enzymes of the differentiated 
vegetable organisms. Some experiments have been made by the 
writer on this point, and though these are very far from complete 
the results obtained so far seem to have sufficient interest for them 
to be communicated to the British Association. 
Diastase being an enzyme which is easy of extraction and capable 
of easy quantitative estimation, has been the one selected. It has 
been prepared for the experiments from ordinary malt. A series 
of experiments has also been carried out on saliva. 
The mode of experiment has been to prepare some extract of malt 
by infusing the ground grains with water or salt solution, and to 
expose half of the quantity to strong light, either solar or electric, for 
varying times. Then measured quantities of the exposed and of the 
unexposed halves have been allowed to act upon thin starch- 
paste (1%) at the temperature of digestion, at about 40°C. or at 
the laboratory temperature. During the action its progress has been 
tested from time to time by adding a drop of each digestion to a drop 
of iodine and noting the resulting colour. When digestion has been 
well advanced, both tubes have been boiled with excess of Fehling’s 
fluid and the resulting precipitate collected, washed, combusted in 
a platinum crucible and weighed as Cu O. 
The extracts have been kept free from bacteria by usings per cent. 
KCy as an antiseptic. 
The preliminary experiments were made with an ordinary fairly 
strong extract of malt. Details of three are subjoined. 
Experiment 1. Fairly strong malt extract, half exposed in white 
glass test-tube to sunlight during two days. The other half exposed 
to same rays, but covered with opaque screen. 
Afterwards both tested with starch-paste. When digestion had 
proceeded for seventeen minutes at temperature 20° C. it was completed 
in the control-tube, but was incomplete in the one containing the 
extract that had been exposed to light. 
Experiment 2. Weaker extract, exposed to diffused light during 
five days, receiving during that time about twelve to fifteen hours 
sunshine. 
Subsequent conditions as in experiment 1. The digestion was 
