GAS DISEASE IN FISHES. ook 
well filled with gas the condition modifies considerably the macroscopic 
appearance of the gill, and in fishes of some size the individual emboli 
may be seen on careful inspection by the naked eye. 
The gas has not been observed in the capillaries of the body, but is 
confined to the larger vessels of the systemic circulation and the gills. 
It does not distend the veins, though bubbles may be seen in them. 
In sculpins in full roe the arteries ramifying over the surface of the 
ovary attract immediate attention by their appearance as pale blood- 
less streaks in contrast with the green background of the ovary and 
the dark red of the veins which accompany them. Gas bubbles may 
be seen in the pyloric cceca, in the walls of the intestine, and also 
within the intestine itself, though these latter may be due to other 
causes. 
CAUSE OF THE GAS DISEASE IN FISHES. 
POSSIBILITY OF INFECTION BY GAS-PRODUCING BACTERIA. 
The inference to which all the gas symptoms at first give rise, of 
infection with gas-producing species of bacteria, has been negatived 
by repeated attempts to obtain cultures from the blood and tissues of 
affected fishes, among both the Woods Hole marine formsand those of 
fresh water. The microscope gives no evidence of infection, and inocu- 
lated culture media remain sterile. The Woods Hole sea water suf- 
fered no unusual pollution and the bacterial count at the intake in 
January and February averaged only 191 per cubic centimeter. The 
rapidity of the pathologic process, furthermore, contraindicates 
infection. 
ABNORMAL GAS CONTENT OF WATER IN WHICH THE DISEASE OCCURS. 
The sea water in which fishes die with these described lesions always 
has an extraordinary gaseous content. At the Woods Hole station it 
had passed through a pumping plant which elevated it to storage tanks 
to provide a gravity flow for aquarium and hatching purposes. Steam 
pumps took the water from the sea through a long suction pipe and 
forced it to a height of about 18 feet into tanks, from which it flowed 
to the aquaria and hatching boxes. At the point of intake the sea 
water was of normal quality and fishes lived in it without unusual 
symptoms. The suction pipe was of wood, had been long in use, and 
by deterioration had developed areas of porosity or open leaks, so 
that air continually gained access to the pipe and could readily be 
demonstrated at the pump, which forced a mixture of water and large 
quantities of air bubbles instead of a solid body of water. Immedi- 
ately upon passing the pump this air and‘water came into a region of 
about 8 pounds hydrostatic pressure in addition to that of the atmos- 
phere, and continued under this pressure through a long stretch of 
level water main. As the sea water was approximately saturated with 
