GAS DISEASE IN FISHES. 357 
atmosphere. But in this mechanically induced supersaturation frag- 
ments of the atmosphere are forced bodily into solution in their 
entirety, and the dissolved content is increased by nitrogen and oxy- 
gen in atmospheric proportions, 79+21, instead of in dissolved pro- 
portions, 67+33. When the excess of these two gases escapes spon- 
taneously from the water the oxygen has about the atmospheric 
relation to the nitrogen, 1. &., about 21 per cent of the total, notwith- 
standing that while in solution the oxygen is more than 30 per cent of 
the total of these two. In other words the excess goes in as air and 
comes out as air. Thus the actual analyses already cited (p. 354) of 
precipitated gas from Woods Hole water, show the proportion of oxy- 
gen to be about as in air. 
Since the blood does not release its supersaturation in this way, it is 
at once suggested that the hemoglobin capacity for oxygen modifies 
the effect of the water so far as the supersaturation with oxygen is 
concerned. It would appear that the corpuscles can take up more 
than the usual amount of oxygen and that the increment is not thrown 
out by the rise in temperature. It remains to study experimentally 
the effect upon fishes of water in which the supersaturation is with 
oxygen alone. Some evidence is afforded by an instance of such a 
supersaturation, naturally occurring, in a pond containing trout. At 
the Cold Spring Harbor Station of the New York Forest, Fish, and 
Game Commission, the springs which chiefly supply the station make 
immediately a shallow pond of considerable size. In the spring of 
1904 the bottom of this pond became heavily overgrown with green 
alow, chiefly with a species of Spirogyra. Presumably from these 
alow, the water about the middle of the pond acquired an excess of 
oxygen of 3c. ¢. per liter, while the nitrogen content remained nor- 
mal, or but slightly in excess. Remote portions of the pond were 
normal in oxygen. Large trout lived in it in good condition and 
showed no gas symptoms, but the fact lacks conclusiveness since they 
had access to normal water, which they doubtless frequented. It is 
probable, however, that a large excess of oxygen is required to pro- 
duce untoward results from this gas alone. In the conditions at Woods 
Hole, while the excess was of both oxygen and nitrogen, 1t is prob- 
able that the damage was done by the latter eas alone. 
RELATION OF GAS DISEASE TO TEMPERATURE AND PRESSURE. 
When water is here described as containing an excess of air, or an 
excess of oxygen or nitrogen, a definite relation of the quantity of gas 
to temperature and pressure is of course connoted. It is hardly 
necessary to insist that dissolved gas only is referred to, for loose 
bubbles present are not really in the water, though they may be 
beneath its surface or within its volume. The gas-disease process, 
then, bears an intimate relation to temperature and pressure. Ifa 
