No. 497] THE BUREAU OF FISHERIES 321 



3. Deaeration of the Laboratory Water Supply.— The 

 "gas disease" of fishes, especially as manifested in the 

 aquaria at the Woods Hole station, has, in past years, 

 been the subject of extensive investigations by Gorham 

 and Marsh. 4 These two writers presented convincing 

 evidence that the cause of this malady lay in the super- 

 saturation of the salt-water supply with air. The latter 

 was shown to be forced into solution under pressure, dur- 

 ing the process of pumping, so that the water which 

 passes into the distributing tanks is "charged" with air, 

 in much the same manner as soda-water and other car- 

 bonated beverages are charged with carbon dioxid. It is 

 a familiar fact that such beverages quickly become "flat" 

 if left to stand in an open vessel ; and that the discharge 

 of the gas is facilitated by agitating the liquid. Marsh 

 found that in this principle lay a ready means of prevent- 

 ing the troubles arising from the super-saturation of the 

 Woods Hole water supply. If the water, before its 

 entrance into an aquarium or fish tank, were allowed to 

 splash through a perforated pan, or merely to fall from a 

 height as a fine jet, the evils of the gas disease would be 

 diminished or altogether prevented. This method has 

 since been generally adopted at the laboratory in con- 

 nection with the large aquaria employed for display pur- 

 poses, as well as with the smaller ones used for scientific 

 experiments. It has commonly been necessary to employ 

 the smallest stream of water practicable, allowing it to 

 fall from a height, and commonly causing it to pass 

 through a perforated pan, or to trickle over a board or 

 other flat surface. Indeed, there have frequently been 

 occasions when a strong stream, introduced beneath the 

 surface of the water in a small aquarium, would prove 

 fatal within a day or less, even to hardy fishes. 



Such a state of affairs has obviously been a serious 

 drawback to the work of the laboratory, which often 



* Bulletin U. S. Fish Commission, Vol. XIX (1899), pp. 33-37; Report 

 U. S. Fish Commission for 1903 (1905), pp. 93-98; Report of the Bureau 

 of Fisheries for 1904 (1905). pp. 343-376. pi. I-III. 



