37 2 Notes . 
completed in thirty-five minutes in the control-tube, but was then 
incomplete in the other. 
Experiment 3. Similar extract. Both exposed to diffused light 
for eleven days ; one tube covered with opaque screen : the two 
tubes side by side in a beaker of water to ensure uniformity of tempera- 
ture. After this exposure both allowed to act separately on starch as 
before. Titrated with Fehling’s fluid after forty-five minutes digestion 
at 40° C. 
The digestion with the extract kept in the dark gave a reduction of 
• 23 gm. ; that with extract exposed to light gave only reduction of 
•092 gm. Cu O. The quantity of extract alone used in both cases 
reduced *083 gm. Cu O. Deducting this from each, D reduced -147, 
L only *009 gm. Cu O ; showing a great impairment of the diastase. 
The next set of experiments was made using the light from a strong 
electric arc-lamp. The solutions of the enzyme were prepared by 
precipitating the diastase from the extract of malt by means of 
30 per cent, alcohol. The precipitate was rapidly collected by 
filtering under pressure, and was dissolved in -2 per cent solution 
of K Cy. When rapidly done, this process yielded a nearly colourless 
solution, which had great diastatic power and which was free from 
sugar and contained a mere trace of proteid matter. 
The first experiments were made by suspending a glass cell in 
which the extract was contained at a distance of two feet from the arc- 
lamp, keeping a control quantity in the dark. 
Contrary to expectation, the diastase was found to be increased in 
amount by the exposure ; in one case from twenty-nine to thirty-two ; in 
another from three to four. Spectroscopic examination of the glass 
showed that it cut off a large proportion of the violet end of the 
spectrum. 
Experiments were then made, avoiding the use of glass, employing 
either agar films, in which the enzyme was suspended, or quartz cells 
containing the fluid extracts. 
The light was found under these conditions to retard the action, as 
in the case of the solar rays of the first set of experiments. 
With the agar films the result was D : L : : 4 : 1. 
With the quartz cell it was D : L : : 12 : 5. 
The beam of light was thus found to have two effects. The rays 
of the violet end of the spectrum were markedly prejudicial, those of 
the red end were on the whole beneficial. 
