60 THE ROYAL SOCIETY OF CANADA 



relationship, but there is certainly no proportionality to the time of 

 immersion. 



We shall deal later with possible causes of the absorption of water . 



The following experiments were carried out in an endeavour to 

 find some data throwing light on the cause of gas retention. 



Experiment 6. Commenced on April 24th, 1915. Ten frogs 

 were placed in the apparatus used in experiment 4, in running Win- 

 nipeg tap-water; the water was at such a height that the frogs could 

 come to the surface to breathe, but that under normal conditions 

 their bodies (excluding the heads) were continuously immersed in 

 water. Frogs were found dead at the bottom of the containing vessel 

 on the first, third, seventh, eleventh, thirteenth, fourteenth, and 

 twenty-first day. None were markedly swollen. On the ninth day 

 of immersion a frog was found dead, floating on the surface, after 

 being buoyant and unable to dive below the surface for four days. 

 It had been removed and measured after being buoyant for two days; 

 its weight was then 59 grams, its volume 62 c.c, (density 0-95). 

 Measured after death, it weighed 67-5 grams, its volume was 70 c.c. 

 (density 0-96), indicating a gas absorption of 2-5 c.c. only. 



At the end of 24 days the three living frogs were removed. One 

 was slightly swollen and not buoyant. The buoyancy of one had 

 been just perceptible for four days, but there was no measurable 

 difference between weight and volume. The third frog was markedly 

 distended, and had been floating at the surface of the water for 11 

 days. Its volume was 70 c.c, its weight 51 grams, (density 0-73), 

 indicating a retention of 19 c.c. of gas. 



The distinctly longer period of buoyancy required for retention 

 of correspondingly large amounts of gas in this experiment, than in 

 those where the frogs were completely immersed is probably to be 

 explained by the fact that as soon as the buoyancy became marked 

 the frogs were forced to the surface, and larger areas of skin were 

 exposed to the air. 



The experiment shows that cessation of lung respiration is in 

 no way responsible for the gas-retention, a result in line with the 

 conclusions of Bohr as to the continuous skin function in respiration 

 in the frog. 



The large number of deaths occurring in this experiment unac- 

 companied by the factors hitherto noted is due, without doubt, to 

 the fact that it was carried on in late spring, when the frogs had been 

 in the laboratory for a long period and when, under normal condi- 

 tions they would have been feeding; it indicated that further exper- 

 iments at this time of the year with laboratory frogs would not yield 



