[cameron-brownlee] gas in TISSUES OF THE FROG 61 



reliable results, and it was among the last performed of the experi- 

 ments described in this paper. 



Winnipeg tap-water is a particularly hard water. The following 

 figures for the solids contained were determined by Dr. H. P. Armes, 

 and furnished to us by Professor M. A. Parker of the Department 

 of Chemistry. The sample was taken on August 29th, 1912 (there 

 is no reason to believe that there has been any noteworthy change 

 of composition in the interval), and the figures refer to parts per mil- 

 lion by weight. 



Free and saline NH3 0-01 



Albuminoid NH3 nil 



Oxygen consumed 0-28 



N as nitrite trace 



N as nitrate 0-05 



Ca 94-0 



Mg 71-2 



Na (calculated) 205-4 



CI 284-0 



SO4 212-1 



Fe 0-05 



Total solids 1158-0 



Temporary hardness 354 



Permanent hardness 172 



The solution corresponds approximately to 0-1 percent NaCl, 

 and has therefore an osmotic pressure one sixth that of the frog's 

 body-fiuid; this suggests at once that the gas retention may be con- 

 nected with this abnormally great amount of solute. Two possible 

 mechanisms suggest themselves, the first, osmosis, the second, a 

 specific pharmacodynamic effect of some constituent of the water 

 on the frog, and presumably on the skin of the frog. The following 

 experiments were carried out to test these possibilities. 



Experiment 7. A bottle was filled with about 4-5 litres of tap- 

 water to which two grams of sodium chloride per litre has been added 

 so that the osmotic pressure of the solution was about three times 

 that of Winnipeg tap-water. A constant stream of air was sucked 

 through a tube reaching to the bottom of the vessel, and the water 

 caused to circulate continually, so that the whole was kept thoroughly 

 aerated. The conditions differed from those in the previous exper- 

 iments by the greater aeration of the water (approximately saturated), 

 its greater osmotic pressure, and also by the fact that the water was 

 throughout at room temperature, i.e., on the average probably at 

 least 10° higher. 



