ON THE POISONOUS ACTION OF DI-CYANOGEN. 
37 
shaking the supernatant liquid was after 24 hours poured off. 
The sediment of yeast was then shaken with 5 c.c. sterilized 
Pasteur’s solution 1 ) and placed in a narrow test-tube. No trace 
of fermentation was observed even at a temperature of 30°C, 
while in the control experiment a vivid fermentation was 
going on after half an hour. In a second experiment about the 
same amount of yeast was mixed with a di-cyanogen solution in 
a dilution of 1 : 5000, respectively 1 : 10000 (30 c.c.), and left to 
stand, being frequently shaken, for 20 hours. The liquids were 
poured off from the yeast and the latter was mixed with 10 c.c. 
of sterilized Pasteur’s solution at 25°C. No fermentation was 
observed after 3 hours with yeast that had been treated with 
di-cyanogen solution of 1 : 5000, but later a few small gas-bubbles 
developed, although even after one day the development of 
gas was very slight, while in the control experiment after 15 
minutes a strong fermentation had set in. On the other hand, 
in the case of the yeast having been in contact with the cyanogen 
solution of i : 10000 only 20 gas-bubbles developed in 1 minute 
after being 15 minutes in Pasteur’s solution at 25°C, but more 
than 200 gas-bubbles were observed in the control case in the 
same duration of time. 
In another experiment it was found that every trace of the 
fermentative action was annihilated after 24 hour’s contact of 
yeast with di-cyanogen solution of 1:2000, while in several ex¬ 
periments with hydrocyanic acid the fermentative action was not 
annihilated. When the yeast was suspended for 24 hours in a 
sugar solution 2 ) containing hydrocyanic acid in a dilution of 
i : 1000, as long as hydrocyanic acid was present no fermentation 
was observed, but as soon as it was removed and the yeast settled 
at the bottom was shaken with plain sugar solution, the fermen¬ 
tation was almost as energetic as in the control mixture. This 
observation confirms those of Schönbein, 1 2 3) Schaer 4) and Liebig 
(1. c.), that hydrocyanic acid of a certain strength will paralyze 
1) Instead of the tartrate of ammonia however extract of meat was used. 
2) This solution contained 5°/ 0 cane sugar, i°/ 0 extract of meat, 0.1 °/ 0 KH 2 P 0 4 
and a trace of magnesium sulphate and was mixed with so much prussic acid that 
the percentage corresponded exactly with the stated amount. 
3) 'Zeitsch. für Biologie 1867, Bd. Ill, S. 142. 
4) Ibid. 1870, Bd. VI, S. 503. 
