194 Thirty-Second Annual Meeting 



The affection may be called a gas disease in consideration of 

 the very plain lesions. But what is the gas, where does it come 

 from, and how did it get free within the vessels? The first 

 thought is of bacterial infection, for many bacteria produce gas. 

 The microscope shows no organisms of this nature in the blood, 

 and moreover, the blood is sterile when examined in bacteriologi 

 cal culture media. Bacteria do not cause the mortality. The 

 explanation now to be offered falls somewhat short of absolute 

 proof, but it explains so plausibly that proof of it is anticipated. 

 The external gas is ordinary air. It does not emanate from th<- 

 fishes themselves, but separates from solution in the water upon 

 their bodies just as it does upon any other solid surface im- 

 mersed in the water. This gas collected from its loose adherenc' 

 to the exterior of the fishes and from the large blisters or vesicles 

 in various parts of the skin, has been examined by the chemist 

 and pronounced air with a slight admixture of carbon dioxide. 

 The gas from within the vessels can not only be easily collected 

 in amount and has not been examined chemically, but in the 

 light of the other facts it is in every way probable that it also is 

 merely air. 



Now inasmuch as any water fit for fishes contains air in solu- 

 tion for their breathing purposes, and they live in it without 

 such startling results as above described, this particular water is 

 of extraordinary quality with regard to the air it holds in solu- 

 tion. The air is in excess; the water is supersaturated with it, 

 and the excess constantly tends to escape in the form of small 

 bubbles which gather on the fishes and other solids, and also in- 

 sensibly at the surface of the water. 



In order to understand how an excess of air gets in solution 

 in the water, why it tends to pass off afterward, and how it has 

 access to the blood of fishes, some general considerations are 

 necessary. Water dissolves gases according to definite laws, tho 

 variable factors influencing solution being temperature and pres- 

 sure. Cold water takes up more air than warm water, and under 

 high pressure more than under low pressure. The waters of na- 

 ture — the sea, lakes, rivers, brooks, etc., — usually, l)ut not 

 always, take up air from their surfaces only, and at the atmos- 

 pheric pressure, which is only slightly variable. Fishes in such 

 waters are ordinarilv accustomed to dissolved air, the maximum 



