EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
149 
However, in spite of this, certain results stand out sharply. In the first place, 
many treated specimens actually died in the liquor solutions. Secondly, those 
specimens which were treated for any considerable length of time with liquor in any 
concentration employed, from 0.5 to 10.0 parts per thousand, and did not die, were 
caused to reduce their normal number of hours per day of feeding, as judged on the 
basis of the activity of the control oysters. 
In all, 19 specimens died as a result of the sulphite liquor solutions to which they 
were subjected. Oysters died after different periods of time in solutions of liquor 
ranging from 0.67 to 10.0 parts per thousand; that is, 1 part liquor to 1,500 to 1 part 
to 100. 
In Figure 32 a graph is given to show the number of days of treatment after which 
specimens died in the series of concentrations employed. Although the points on the 
graph are widely distributed, they 
appear to fall into a sort of curve 
of the general form of those pre- 
sented in Figure 31 for the sensory 
reaction. There are too few points 
to allow such an analysis as might 
permit the prediction of the length 
of time required for death to occur in 
even lower concentrations of liquor 
than those employed. There is a 
striking difference between the death 
time of oysters in 10 parts per thou- 
sand and that of specimens in about 
1 part per thousand. Naturally, as 
the concentration is lowered the 
death time increases toward in- 
finity. It is impossible to predict cer- 
tainly from this whether 0.1 part per 
thousand, for example, would kill 
oysters, but it is obvious that, should 
it do so, it would on the average re- 
quire considerably over 30 days. 
Only one specimen died much more quickly than the others, in respect to the 
concentration used. This was the specimen treated with a solution of 6 parts per 
thousand which died at the end of two days. The graph (fig. 32) clearly shows, 
also, that death of all these specimens was due to a particular variable factor in the 
water. If due to any variable other than the sulphite liquor the points in the graph 
would be scattered in all directions, regardless of the concentration of liquor used. 
Further, that the control specimens lived, and grew, and fed well under laboratory 
conditions demonstrated that these conditions were certainly not unfavorable. 
If the death periods of oysters treated with different concentrations of sulphite 
liquor be plotted in such a manner as to take into consideration the differences in 
activity of the specimens, a somewhat more complete picture is obtained. In order 
to do this (fig. 33) the record of each specimen which died was analyzed and the 
number of hours per day that it remained open computed as percentage of the 24-hour 
period. The product of this value (average percentage of the time open) multiplied 
by the number of days required for death, is then considered to represent total effect 
0 I 23456789 10 
CONCENTRATION OF LiquORIN PARTS PER THOUSAND 
Figure 32.— Time required for death in solutions of sulphite liquor in the 
series of concentrations. The points in general show that the death 
time increases with diminishing concentration. See Figure 33 and 
Table 3 
