GAS DISEASE IN FISHES. 351 



well filled with f^as the condition modifies considerabl}^ the macroscopic 

 appearance of the gill, and in fishes of some size the individual emboli 

 ma}' be seen on careful inspection bj the naked eve. 



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 bu])bles may be seen in them. 

 In sculpins in full roc the arteries ramifying over the surface of the 

 ovar}' attract immediate attention by their appearance as pale blood- 

 less streaks in contrast with the green background of the ovar}- and 

 the dark red of the veins which accompany them. Gas bubbles ma}' 

 be seen in the pvloric cceca, in the walls of the intestine, and also 

 withiH the intestine itself, though these latter ma}' 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 forms and 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 AVATER 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 fiow 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 

 symptouLS. 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. Inmiedi- 

 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 



