Thomas. — Effects of Certain Oils Upon Brook Trout 133 



It can easily be seen that except when in mere traces most 

 of the creosotes are highly toxic. In experiments where the water 

 containing the creosotes was aerated for a few days before the fish 

 were put into it, the fish lived much longer than when put in before 

 aeration, thus showing that aeration had decreased the toxicity. 

 When a second fish was put in a solution in which one had 

 previously died, it would live longer than the first fish. This 

 may have been because some of the creosotes had been absorbed 

 by the fish first placed in the solution, thus the concentration 

 reduced, or the toxicity may have been decreased by aeration. 

 Fish from creosote solutions had a strong odor of the oil. The 

 flesh even after being cooked, tasted of creosote. 



To ascertain the effect on fish of wood after treatment with 

 creosotes the following method was employed. Strips of wood 

 about one square centimeter cross-section were painted with a 

 thick coat of creosote and hung to dry in an unheated room for 

 nineteen days. The temperature of the room, observed during 

 the day, ranged from about 10° C. to about 20° C. 



After drying, the strips of wood were anchored in jars of 

 water, where they assumed a position not unlike that of spar- 

 buoys. The anchors were made by sealing mercury in glass 

 tubes. These were tied to the strips of wood by means of cotton 

 cord. In this way no metal or other interfering substance was 

 introduced into the water. The painted surface of the strips 

 exposed to the water was about thirty or thirty-five square 

 centimeters. 



The strips were weighed before and after treatment with the 

 creosote and also after drying. From two to five-tenths of a gram 

 of the creosote adhered to each strip, depending upon the viscosity 

 of the individual substance. From a half to an eighth of the 

 weight of the creosotes was lost upon drying. 



The strip treated with creosote from coal-tar killed the fish 

 is about twenty hours. The one treated with the product dis- 

 tilling between 295° C. and 320° C, killed the fish in three days. 

 The others produced no effect at all upon the fish in a week. The 

 fish did not refuse food either. 



A possible cause for the death of the fish in the two instances 

 mentioned might have been that the creosotes had not thoroughly 

 dried and hardened before the strips were immersed in water. 

 Time did not permit repetition of the experiments. 



