jan. i5 ,1925 Further Studies on Toxicity of Extracted Onion Juice 179 
Table II.— The effect of heat on the toxic volatile substances in onion juice as deter¬ 
mined by their effect upon Colletotrichum circinans 
Treatment of 
juice 
Response of fungus to exposure to 
juice heated for various intervals 
Response of 
fungus to 
unheated 
juice and 
to control 
medium 
Source of 
volatile 
Method of exposure of 
fungus 
✓—* 
d 
Percentage of 
germination 
Average length 
of germ tubes 
(microns) 
oils 
• 
Method of 
heating 
© 
3 
© 
S-H 
a 
a 
£ 
15 minutes 
30 minutes 
60 minutes 
90 minutes 
15 minutes 
30 minutes 
60 minutes 
90 minutes 
Germination 
(per cent) 
Average length 
germ tube 
(microns) 
Five drops placed in moist 
[Reflux.... 
(70 
99 
99 
99 
98 
52 
39 
69 
81 
chamber. 
\96 
100 
99 
99 
99 
76 
68 
108 
91 
[Open heat. 
(70 
99 
99 
98 
99 
51 
62 
64 
87 
. 
Heated 
\96 
99 
99 
99 
99 
75 
86 
93 
93 
juice. 
] One drop of juice placed 
f Reflux_ 
(70 
0 
0 
0 
0 
0 
0 
0 
0 
in one drop of onion de- 
\96 
0 
0 
0 
0 
0 
0 
0 
0 
1 
coction spore suspen- 
[Open heat. 
(70 
0 
0 
0 
0 
0 
0 
0 
0 
j- 
sion. 
\96 
0 
0 
0 
0 
0 
0 
0 
0 
Five drops placed in moist 
None. 
76 
10 
o 
Unheated 
chamber. 
One drop of juice placed 
in one drop of onion de¬ 
coction spore suspen¬ 
sion. 
on decoction spore suspen- 
None.. 
! 
0 
juice. 
Control oni 
None. 
| 
| 
( 
99 
109 
sion. 
' 3 
j 
a decidedly destructive effect upon the 
volatile toxins. Both distillate and 
residue were practically devoid of vola¬ 
tile toxins, and the former contained a 
much reduced amount of dissolved 
toxin. It appears that the toxicity is 
due to at least two components, one of 
which is readily volatile and the other 
less so or not as all. The volatile 
toxins are largely broken down by 
boiling, while the toxic property of the 
residue is not destroyed by heat. This 
is in accord with the generally accepted 
view that onion oil is decomposed by 
distillation at ordinary pressure (-4). 
Table III.— The 
TEMPERATURE DURING THE TEST. 
Certain irregularities in the results led 
the authors to suspect that the tempera¬ 
ture during the experiments influenced 
the effect of the volatile substances 
upon the spores. Two sets of relations 
are to be considered: First, that of 
temperature to spore germination and 
growth; and, second, that of tempera¬ 
ture to the volatilization of oil from the 
onion juice. The first set of conditions 
for Colletotrichum circinans has been 
studied previously by the senior author 
(6 ). It was shown that the rapidity of 
effect of distillation on the toxic substances in expressed onion juice , 
as determined by tests with spores of Colletotrichum circinans 
Method of exposure of fungus 
i 
Source of volatile 
oils 
Response of fungus 
spores 
Per cent 
germi¬ 
nation 
Average 
length of 
germ 
tubes 
(microns) 
5jirops placed in moist chamber.. 
(Distillate.. . 
100 
100 
76 
94 
0 
0 
99 
94 
95 
10 
18 
0 
0 
109 
^ Residue. __. 
1 drop of liquid added to 1 drop of onion-decoction-spore suspen¬ 
sion. 
Control onion decoction spore suspension.. 
lUnheated juice.... 
[Distillate_ 
■(Residue.. 
lUnheated juice_ 
