THE GAS-BUBBLE DISEASE OF FISH AND ITS CAUSE. 
35 
Other experiments, indicated in the following table, were made: 
Fish. 
Total length of 
time subjected 
to reduction of 
atmospheric 
pressure. 
Results. 
Scup (5 cm. long) 
Mrs. 
1 
Mins. 
0 
Bubbles in eyes. 
Same fish 
i 
0 
Bubbles enlarged ; eyes protrude. 
Soup (5 cm. long) 
1 
12 
One eye shows bubbles and hemorrhage. 
Bubbles on pectoral fin and on “feelers. ” 
Sea-robin (6 cm. long) 
3 
49 
Sea-robin (6 cm. long) 
0 
14 
Bubbles on lower jaw. 
Puffer 
4 
4 
Bubbles on tail. 
Minnow ( Cyprinodon variegatus) 
6 
0 
No change. 
Normal fish were kept as controls in all cases and showed no change. Whenever 
scup were subjected to this reduction their eyes were affected first; bubbles formed 
and the eyes protruded in much less time, but in exactly the same way as in scup 
placed in the aquaria. In the young sea-robins bubbles appeared on the pectoral fins 
and on the finger-like appendages, while in the young puffers they appeared at the 
base of the tail. In all these cases the parts first affected were the same as those 
subject to the disease in the aquaria. The minnows unaffected in the aquaria were 
unaffected by the removal of the atmospheric pressure. 
Now, the question naturally arises, will the increase in pressure improve the 
condition of the fish already suffering from the disease? Small scup taken from 
the aquarium, already showing protrusion of the eyes and bubbles on the head and 
fins, were subjected to a pressure equal to 10 feet of water. In 24 hours many of the 
bubbles had disappeared, and the eyes had returned to their normal condition. 
Under this treatment puffers recovered from a decidedly diseased condition in 24 hours. 
The data of these experiments may be tabulated as follows: 
Fisb. 
Length of time 
subjected to 
pressure of 16 
feet of water. 
1 
Results. 
Scup with bubbles on head 
Scup with protruded eye 
Scup with bubbles on head and protruded eye 
Puffers (3.5 cm. long). Bubbles at base of tail 
Puffer (3.5 cm. long). Bubbles on dorsal fin 
Puffer (3.5 cm. long) . Bubbles on eye and on fin 
Puffer (3.5 cm. long). Large bubble under right fin. 
Sours. 
24 
24 
24 
24 
24 
24 
24 
Bubbles disappeared. 
Eye nearly normal. 
Entirely normal. 
Do. 
Normal. 
Eye nearly normal. Bubbles 
on fin disappeared. 
Normal. 
Control animals checked the results of these experiments. 
In both the reduced and the increased pressure experiments above tabulated 
young fish were used, but whenever adult animals were employed similar results were 
obtained. 
The change in pressure which fish must undergo when transferred from the ocean 
to aquaria is not small in amount. We have only to consider that at the surface the 
pressure is about 14.7 pounds per square inch, and that for every foot in depth it 
increases at the rate of 0.445 pound per square inch. At a depth of 5?} fathoms the 
pressure is just double that at the surface, and at a depth of 300 fathoms it would 
amount to over 800 pounds. 
