30 
BULLETIN 227, U. S. DEPAETMEXT OF AGRICULTURE. 
nornial growth is also relatively slow as compared with that of the 
other organism. Sometimes on high concentrations of toxic media 
the fungus would remain dormant from four to seven weeks and then 
begin a slow development. For this reason it has been difficult in 
many cases to find the exact inhibition point of a preservative with- 
out carrying out a large number of long-continued tests. 
On the other hand, Fomes pinicola seems rather sensitive to slight 
changes in concentration, and one can usually judge within a month 
whether the fungus will develop. 
The difference in behavior between these two organisms shows 
how very necessary it is to make only qualified statements when dis- 
cussing the relative toxicity of preservatives toward fungi. We have 
at present no satisfactory way of predicting, except by trial, how a 
given preservative will react on different organisms. 
A direct comparison of toxicities, as given in Table II, shows that 
in many cases essentially the same order holds, but there are several 
exceptions. Fractions I and IV of coal-tar creosote and zinc chlorid 
being the most conspicuous. 
In Table III the oils used are grouped according to their nature, in 
order to show a direct comparison between wood tar, coal tar, water- 
>gas tar, and petroleum products. 
Tabl] 
III. — List of icood-preseri'ing oils tested, showing relation between their specific 
gravities, boiling points, and toxic properties. 
[Results marked w 
ith an 
asterisk (*) are approximately correct. 
] 
Preservative. 
Specific 
Percentage distilling below— 
Killing point (per 
• cent). 
gravity.* 
180° 
C. 
215° 
C. 
245° 
C. 
275° 
C. 
305° 
C. 
320° 
C. 
360° 
C, 
Fomes 
annosus. 
Fomes 
pinicola. 
Wood tar (hardwood) 
Wood creosote (Douglas fir). 
United Gas Improvement 
Co. 1.07 oil, Xo. 1101 
Water-gas tar distillate >.'o. 
2235 
1.195 *°7 
*31 
*31 
*10 
12. S 
17.8 
78.3 
30 * 
.9 
51 
54.7 
37.7 
44.4 
*1.25 
*.65 
40+ 
*. 65 
.55 
.30 
0.75 
1.052 
1.058 
.995 
1.048 
.934 
1.003 
1.045 
1.088 
1.150 
1.126 
1.127 
.937 
*16 
3.3 
4.8 
35.1 
*2-3 
*.20 
16.3 
61.7 
54.1 
*22 
75.3 
67.2 
*27 
80.3 
74.1 
56.4 
40+ 
Coal-tar creosote: 
Grade C 
.225 
.225 
*S0 
16.2 
.9 
*92 
49.2 
4.7 
77. 7 
38.5 
4.1 
16.4 
85 
54.3 
10.1 
*29 
*30 
30.2 
~48.Y 
*80 
*325 
*3.30 
*33 
5.25 
4.5 
40 
.125 
*125 
*7.8 
Avenarius carbolineum (sp. 
gr. at 15.5° C.) 
S. P. F. carbolineum (sp. 
gr at 16° C ) 
1.1 
2.6 
*9 
*3 
6.1 
.30 
Copperized oil (sp. gr. at 
25° C.) 
*2 
*10 
*22 
40+ 
i At 60° C. except as stated for the last three preservatives. 
It is interesting to note that the wood-tar and low-boiling water- 
gas tar and coal-tar distillates tested show very similar toxic prop- 
erties, while the carbolineums, which consist in the main of the 
high-boiling constituents of coal-tar creosote, in all cases proved 
much less toxic to the fungi used. 
