EFFECT OF CRUDE OIL POLLUTION ON OYSTERS 
187 
gravity of tlie water (at 17.5° C.) at the beginning and at the end of this period 
was 1.02455 and 1.02461, respectively. This slight increase in the specific gravity 
may be attributed either to the evaporation of water or to the dialysis of substances 
present in the oil. 
An oyster was mounted in the usual manner and placed in a celluloid tank of 
1,830-cc capacity used for measuring the rate of flow of water through the gills. 
Water was supplied at the rate of 100 cc per minute and the entire volume of the tank 
could be renewed in 20 minutes. Drops of water filtered by the oyster gills were 
recorded by means of an electric drop counter. The record of this experiment is 
presented in table 15 which shows the average number of drops per minute deliv- 
ered by the gills before, during, and after the addition of the water soluble fraction 
of the oil. During this period the temperature varied between 21.5 and 21.8° C. 
Table 15 . — The effect of water soluble fraction of Pelto oil obtained by dialysis through a collodion 
membrane on the rate of flow of water through the gills of the oyster 
Time 
Drops per 
minute 
Remarks 
Time 
Drops per 
minute 
Remarks 
12:05-2:25 
•208 
Sea water. 
4:07-4:08 . 
105 
Sea water replaced by solution — 
2:30 
Solution turned on. 
Continued 
2:50 
96 
Sea water replaced by solution. 
4:08-7:10 
2:53-2:54 
96 
Do. 
7:10-7:11 
53 
Solution turned on. 
3:20-3:21 
90 
Do. 
7:11-7:12 
52 
Do. 
3:22-3:23 
66 
Do. 
7:12-7:13 
60 
Do. 
3:23-3:24 
90 
Do. 
7:15 
3:24-3:25 __ 
108 
Do. 
7:50-7:51 
99 
Do. 
4:00-4:01 
10 
Do. 
4:01-4:02. 
14 
Do. 
NEXT DAY 
4:03-4:04 
72 
Do. 
4:05-4:06 
106 
Do. 
9:15-9:16.. 
66 
4:06-4:07 
107 
Do. 
1 Average. 
By examining this table one notices that the presence of the water soluble 
fraction of Pelto oil greatly interferes with the normal activity of the gill epithelium. 
The rate of flow of water becomes less regular and decreases about 50 percent. A 
3-hour exposure in this solution causes further inhibition of the ciliary motion of 
the epithelium, the activity of which was not fully restored even when the oyster 
was placed back in natural sea water. 
On account of the limited amount of crude oil available in the laboratory experi- 
ments, it was necessary in preparing the water soluble fraction to use the same sam- 
ple of oil several times. It was noticed that subsequent 30-minute stirrings of 2 
volumes of crude oil with 1 volume of sea water did not exhaust the potency of the 
sample in inhibiting the work of the ciliated epithelium. Table 15 shows the per- 
centage of depression in rate of flow of water caused by 10-, 20-, and 40-percent 
solutions of the extract. It will be observed that after 28 washings, there was no 
decrease in the toxicity of the extract. 
Table 16 .- — Showing no decrease in toxicity of a sample of oil due to repeated washings with sea water 
Number of washings 
Percent de- 
pression 
Number of washings 
Percent de- 
pression 
Number of washings 
Percent de- 
pression 
10 PERCENT 
20 PERCENT 
40 PERCENT 
2 
6.7 
1 
17.0 
4 
50.0 
19 
10.3 
1 
69.5 
9 
54.3 
28 
29. 1 
8 
34.0 
9 
70.5 
8 
80.6 
10 
79.0 
13 .. 
68.0 
16 
45.0 
22 
77.0 
25 
35.0 
