558 



to live more or less normally in water that had become alkaline either 

 from treatment or from the using up of the COo, both free and half 

 bound, by the algae growing in the water. However, it is still to 

 be demonstrated that there are any species of truly fresh-water fishes 

 that can reproduce successfully in water that is decidedly alkaline to 

 phenolphthalein throughout the year. 



It should not be concluded that, since a certain small amount of 

 CO2 seems to make the water more acceptable to certain fresh-water 

 organisms, it will be well to add this gas to natural waters, for all the 

 carbon dioxide that is necessary to organisms living in nature is pro- 

 duced in the natural waters by the decomposition of organic materials 

 contained therein; and, in fact, the processes of decay often raise the 

 concentration of carbon dioxide to a point where it is detrimental, 

 and even fatal, to the aquatic inhabitants of the water. The addition 

 of anv substance, therefore, which will increase the amount of carbon 

 dioxide in these waters, must be looked upon as detrimental ; and it is 

 certain that were carbon dioxide the only toxic substance contained 

 in gas-house waste, the effect of this waste upon the aquatic organisms 

 would still need to be regarded with suspicion, for while the more 

 hardv organisms might survive its presence the less resistant species 

 would be sure to fare badly, at least near the point of introduction. 



Carbon monoxide — which differs from the dioxide in that the car- 

 bon atom in the monoxide is holding in combination but one oxygen 

 atom instead of two and is, therefore, chemically speaking, unsat- 

 urated — is a VvcU-known poisonous gas^ and its frightfully deadly 

 effect when present in the atmosphere in even exceedingly small 

 quantities has been vividly demonstrated by many investigators. Two 

 to three per cent, of carbon monoxide in the air breathed by a mouse 

 will cause the death of the animal in from one to two minutes. The 

 familiar poisonous effects of illuminating gas are largely due to the 

 comparatively large per cent, of carbon monoxide which it contains. 



The investigation of the toxic properties of the two gases in ques- 

 tion was carried on as follows. The work with carbon dioxide as 

 summarily presented here has been carried on since 19 12, partly at the 

 University of Chicago and partly at the University of Illinois. The 

 carbon-monoxide investigations have all been carried on in the labora- 

 tory of the State Laboratory of Natural History at the University of 

 Illinois, and with facilities which constitute a part of the equipment 

 of the \'ivarium. The results show that both gases are toxic to 

 fresh-water fishes in the concentrations which would result from the 

 introduction of gas-house wastes into natural waters, and that carbon 

 monoxide is by far the more deadly, killing the most resistant fishes 



