240 HAROLD D. CLAYBERG. 



some of 2- and 5-liter were also utilized. The fish was placed 

 in the solution after being measured and weighed; and the time 

 till its behavior became definitely abnormal and the time till 

 death were carefully noted. 



2. Results with the Minnow (Pimephales) . Preliminary work 

 was undertaken looking towards a comparison of the closed 

 bottle method of killing (used in all drug standardization work) 

 with that of running poison of known concentration at definite 

 rate through a bottle. The results indicated that the two 

 methods had like effect for the same poison concentrations- 

 Further, the results showed that the hour killing concentration 

 for the minnow was between 2.2 and 2.3 c.c. per liter for ether 

 (1,584-1,586 mg.). Weight used varied from 1.5-4 grams. 



3. Ether: The Sunfish.- The standard used by Shelf ord for 

 the measurement of toxicity of poisonous polluting substances is 

 the concentration of any poison sufficient to kill a 4-5 gram 

 Lepomis humilis in approximately 60 minutes. The hour killing 

 concentration for ether was found to be between 3.685 and 

 3.690 c.c. per liter (2,653.2-2,656.8 mg.). Apparatus at hand 

 permitted no closer determination. The number of experiments 

 run was sufficient to plot the death curve shown in chart II. 

 The base line or X-axis was used for minutes until the fish be- 

 came abnormal or dead. The Y-axis was used for the concen- 

 trations employed. Points for all experiments were plotted 

 and these were connected to form a curve. This curve showed 

 a certain width due to variation in time of death throughout, 

 which has been brought out by stippling. 



The data were now separated into three classes to enquire 

 into the effect of fish weight on death time. Since not enough 

 fish of strictly standard size could be obtained, fish of size be- 

 tween 2 and 25 grams were used. Those obviously outside the 

 weight from external appearance were used to determine the 

 critical concentration roughly and those nearest the proper 

 standard were used last. These were now placed in three classes: 

 class i, 2-9 grams; class 2, 10-19 grams; class 3, 20-25 grams. 

 These were plotted in three curves on chart II. Those of 

 classes I and 2 were complete enough to show the following facts. 



At about 4.8 c.c. per liter (3,456 mg.) the fish of the two classes 



