GAS DISEASE IN FISHES. 355 



The quantities actually dissolved in the water were tii'st 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 III, 

 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 ox\-gen by oxidation, and there may have 

 been an original excess of this gas as well as nitrogen. 



Eiimiiuitian of the disease hy reducing gas content of vxiter. — The 

 replacement of the old suction pipe with a new im'pervious one abol- 

 ished all signs of the gas disease at Woods Hole. Determinations made 

 upon the water of the aquarium after air had been intentionalh' admit- 

 ted to this new suction pipe showed definite and considerable excesses 

 of both nitrogen and ox3"gen, these determinations being made at 

 the station upon freshl}' taken samples. The gas was boiled from 

 the water by the Tiemanu and Preusse modification of Reichardt's appa- 

 ratus (Hempel, 1902, p. 10) and determined b}^ absorption, the residue 

 after removal of carbon dioxid and oxygen being considered as nitro- 

 gen. There appeared an excess of both nitrogen and oxj'gen of some 

 3 to 6 c. c. per liter of water in the case of nitrogen, and of 1.5 to 2.6 

 c. c. of ox3"gen. This condition of the water killed 6 hake in from 8 

 to 20 hours. The figures are probably somewhat g'reater than those 

 for the conditions of the old leaking suction pipe, which may be repre- 

 sented bj^ an excess of about 2 c. c. of nitrogen per liter, and of some- 

 what less than 1 c. c. of oxj'gen. 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. Tlie dead 

 fishes showed all the described lesions and s^'mptoms. It is left beyond 

 question that the gases of the pure atmosphere are one of the efficient 

 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 rapidit}" dependent on the degree 

 of this exposure. Yv'henever b}^ 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, carr^^ing in many bubbles of free air, the lesions on the fishes 

 were more slowlj^ produced, and the fatal result was postponed. The 

 process of exposure deaeratecl the water, and had onh' to be made 

 thorough enough to correct it completel}' 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 



