70 BULLETIN 1036, U. S. DEPARTMENT OF AGRICULTURE. 
pounds, the toxicity increases with molecular weight and with rise 
in boiling point. Russell and Pendleton (32) have shown that both 
pyridine and quinoline are valuable for soil sterilization. 
It is realized that these tests on the various constituents of coal-tar 
creosotes are not conclusive proof of the antiseptic action of these 
materials when they are applied to timber-destroying fungi. The 
tests do at least point out the way in which it is most probable that 
creosote produces its toxic effect, and it might reasonably be assumed 
that the various classesof compounds, when applied to fungi, will 
behave in much the same way as they did in the tests in which they 
were applied to various other lower organisms. This will be the more 
probable if the general conclusion can be substantiated by a consider- 
able amount of data. Certain tests now being made at the Forest 
Products Laboratory show that the tar acids are extremely toxic to 
timber-destroying fungi; that the tar bases are as toxic to these 
fungi, if not more so; and that the higher hydrocarbons under test 
have at best a slight toxicity. It seems, therefore, that the conclusion 
is justified that creosote oil in a large measure owes its toxicity 
against timber-destroying fungi to the tar acids and tar bases which 
form a small part of its composition, the rest of the toxic effects 
being caused by the light oil. The heavier oils have but little toxic 
value for this purpose. This conclusion is further brought out by 
the curve (fig. 36) showing the toxicity of coal-tar creosote plotted 
against its volatility at 275° C. 
TESTS ON MARINE BORERS. 
Practically the only work of this nature on the toxicity of creosote 
and its constituents toward the marine borer that has been published 
is that of Dr. Shackell (40). He showed that the phenols were 
extremely poisonous to the Xylotrya, but that the hydrocarbons, 
naphthalene, and anthracene could apparently be taken in and 
ejected from the body of this marine borer with no ill effects upon the 
animal. In conformity with tliis result, he found that the lower 
fractions of creosote are more toxic, and that, as the boiling points of 
the fractions increase, the toxicities decrease. 
COMPARISON WITH SERVICE TESTS. 
It is of considerable interest to compare the results of toxicity 
tests with service tests on the same material. Fortunately, there is 
in the Forest Products Laboratory a series of fractions of coal-tar 
creosotes which have been tested by the Petri-dish tests for fungi, 
by laboratory tests for Xylotrya, and by service tests as piling. 
Table 26 shows such a comparison. 
