78 



reaction. According to what has been found in the preparation of 

 nucleinic acid from Saccharomjces cerevisiae we might expect the 

 above mentioned precipitate originated by the addition of 5 perc. 

 HjSO^ to contain nucleinic acid (similar reactions I achieved after- 

 wards also with commercial beer-jeast). 



That the nuclease of yeast-cells is of itself capable of splitting up 

 this nucleinic compound and to set free phosphoric acid may now 

 clearly be demonstrated. A suspension of the washed precipitate in 

 1 perc. glycose and 0,05 perc. MgSO^ inoculated with Torula monosa 

 does not give a phosphate-reaction; but this reaction is obtained 

 when the yeast-cells are ground with quartz-sand and are then 

 brought in contact with a suspension of the precipitate in water. 

 After an incubation at 20° for 48 hours (with addition of a grain 

 of thymol) a distinct phosphate-reaction with Mg-mixture takes place, 

 which is absent in the precipitate itself (also after 48 hours) 

 and is likewise absent in the ground Torula-cells. The impractibility 

 of demonstrating the nuclease-action in the living cells by the 

 phosphate-reaction is probably due to the fact that these cells 

 immediately seize upon the phosphate they have isolated from 

 the nucleinic acid. By crushing the cells, however, we were 

 in a position to prove the nuclease-action of Torula monosa. 

 It appears that this enzymic activity was not lost in the 

 cultures grown without volutin, for with these also phosphate 

 could be isolated from the nucleinic acid precipitate after grinding 

 the cells with quartz-sand. I had ascertained beforehand that among 

 thousands of cells at the most a single vol u tin-containing cell was 

 present in coverslip-preparations of this culture. 



Volutin is separated from the yeast-cells by — NaOH while by 



the same process a nucleinic acid compound is thrown into solution. 

 Though all this seems to point to the identity of these two sub- 

 stances, the decisive proof is furnished only when observing that 

 phosphate-free cultures, not containing any volutin and extracted with 



— NaOH, do not yield a precipitate with 5 perc. H^SO,. 

 it) 



This was evidenced by me in the following way. Twenty-five 

 culture-tubes with volutin-free Torula monosa (at most one granule 



of volutin per field of thousands of cells) were treated with — 



15 



NaOH, and the filtrate was passed through a filter by suction. With 



1 cc. 5 perc. H,SO, per 10 cc. of filtrate at most a trace of turbidity, 



never, not even after centrifugalizing, a precipitate was produced. 



