222 VICTOR E. SHELFORD AND W. C. ALLEE 



Notropis, Lepomis, Umbra and Ameiurus. No bubbles devel- 

 oped in Abramis but they were experimentally produced on 

 several occasions. A typical experiment consisted of raising the 

 temperature of the water from 8 to 17°C. without loss of gas, 

 and allowing it to flow into an aquarium. This gave a large 

 excess of gas. Nine out of seventeen fish developed the disease 

 in nine hours; four of these did not recover. The fishes of a 

 standing water control at the same temperature, showed no 

 signs of the disease. The cure of gas bubble disease was accom- 

 plished by bubbling gases through water in which diseased fish 

 had been placed. Two Hybopsis and one each of Notropis, 

 Catostomus and Ambloplites were cured of the disease in eighteen 

 hours, by the bubbling of oxygen through a tall jar which con- 

 tained the fishes. Two Umbra with large bubbles in their fins 

 were placed in water through which nitrogen had been bubbled 

 for thirty hours and the bubbling continued. Both fish were 

 entirely cured in twenty-two hours. Table 3, experiment 3, 

 shows that, making a very Uberal allowance for exposure to the 

 atmosphere, the nitrogen was probably increased 2 cc. per Uter; 

 (compare table 2). On another occasion, two Hybopsis which 

 were badly affected, were cured in twenty-four hours in the same 

 manner (table 3, experiment 4). Two Ambloplites and four 

 Abramis were kept in water through which nitrogen was bubbled, 

 for twenty-three hours, and neither showed signs of gas bubbles 

 upon dissection, though one died of asphyxia due to the low 

 oxygen content, 0.5 cc. per liter (table 3, experiment 5). 



We find in these experiments no suggestion that fish develop the 

 disease as a result of a simple increase of gas when one gas is dis- 

 placed by another, under one atmosphere of pressure, but rather 

 that the disease appears only where the gases are so much in 

 excess that bubbles collect on any rough or warm object in the 

 water. This excess may be due to a rise in the temperature of 

 the water or a decrease in pressure, or both. It is probably 

 essentially a laboratory disease (Birge and Juday '11, p. 134). 



