GAS DISEASE IN FISHES. 355 
The quantities actually dissolved in the water were first determined 
from a sealed and transported sample taken in September during the 
progress of the disease. The results are probably not perfectly accu- 
rate, because of the age of the sample. By reference to Table II, 
page 373, it is seen that this water had an excess of nitrogen of 2.2 c. c. 
per liter, and was a little less than saturated with oxygen. The time 
which elapsed between the taking and the determination of the sample, 
however, probably removed oxygen by oxidation, and there may have 
been an original excess of this gas as well as nitrogen. 
Elimination of the disease by reducing gas content of water.—The 
replacement of the old suction pipe with a new impervious one abol- 
ished all signs of the gas disease at Woods Hole. Determinations made 
-upon the water of the aquarium after air had been intentionally admit- 
ted to this new suction pipe showed definite and considerable excesses 
of both nitrogen and oxygen, these determinations being made at 
the station upon freshly taken samples. The gas was boiled from 
the water by the Tiemann and Preusse modification of Reichardt’s appa- 
ratus (Hempel, 1902, p. 10) and determined by absorption, the residue 
after removal of carbon dioxid and oxygen being considered as nitro- 
gen. There appeared an excess of both nitrogen and oxygen cf some 
3 to 6c. c. per liter of water in the case of nitrogen, and of 1.5 to 2.5 
ce. c. of oxygen. This condition of the water killed 6 hake in from 8 
to 20 hours. The figures are probably somewhat greater than those 
for the conditions of the old leaking suction pipe, which may be repre- 
sented by an excess of about 2 c. ¢. of nitrogen per liter, and of some- 
what less than 1c. c. of oxygen. The water under the experimental 
conditions referred to with the new suction pipe had exactly the same 
‘effect upon fishes as the water during the service of the pervious 
,wooden suction pipe, save that it was more rapidly fatal. The dead 
fishes showed all the described lesions and symptoms. It is left beyond 
question that the gases of the pure atmosphere are one of the efiicient 
factors in the causation of the gas disease. 
Exposure of the water to the atmosphere at atmospheric pressure 
removes the excess of air with a rapidity dependent on the degree 
of this exposure. Whenever by the mechanical arrangement of the 
delivery pipes at the aquaria the inflow of water was exposed, as when 
a strong jet was allowed to impinge upon the surface of the aquarium 
level, carrying in many bubbles of free air, the lesions on the fishes 
were more slowly produced, and the fatal result was postponed. The 
process of exposure deaerated the water, and had only to be made 
thorough enough to correct it completely by removing the excess. 
Thus, if the inflow was made to pass through a strainer elevated several 
feet above the aquaria, so that the water was divided into many very 
slender streams, which compelled intimate contact with the air during 
