[cameron-brownlee] gas in TISSUES OF THE FROG 63 



removed on the fifteenth day. It was apparently normal, and re- 

 mained so for the following several days during which it was kept 

 under observation. 



Experiment 10. Commenced May 4th, 1915. About eleven 

 grams of hydrated sodium sulphate were dissolved in five litres of 

 water, giving a solution containing about three times the number 

 of sulphate ions as are present in Winnipeg water. Four frogs were 

 immersed in this solution. The water was changed on the sixth day. 

 Frogs died on the seventh, eighth, and two on the ninth day. All 

 were markedly swollen. None showed any trace of buoyancy. 



These preliminary experiments to test whether any particular 

 ions cause the gas retention have led therefore to no positive results. 



Sulphate ions seem to produce a definite toxic effect. The 

 results for calcium ions were not so certain. 



We do not wish to discuss the osmotic phenomena concerned 

 with the absorption of liquid through the skin of the frog. The results 

 summarised in the following paragraphs have however some connection 

 with our own, and are therefore mentioned. 



Weymouth Reid gives in Schafer's Text book^ an account of his 

 own experiments showing that, with living skin from the frog, the 

 direction of easier osmotic flow of non-deleterious solutions is from 

 without inwards; as its vitality declines, the skin becomes less and 

 less permeable from without inwards, and the dead skin is more per- 

 meable in the reverse direction. The first period lasts from 70 to 

 80 hours in strong frogs after somatic death and only 24 hours or so 

 in feeble animals at the end of the breeding season. Reid showed 

 also that when freshly removed skin was immersed in 0-6 per cent, 

 sodium chloride solution, with equal pressure on both sides of the 

 skin so that filtration and osmosis played no part, there existed a 

 current flowing from the outer to the inner surface of the skin. These 

 experiments were carried out in 1890 to 1892. 



Hober, writing in 1907, ^ and basing his remarks largely on Reid's 

 experiments, pointed out that frog's skin was until that time the only 

 membrane in which an absorption-power (resorbierende Triebkrâfte) 

 which could be traced to the epithelium, was demonstrable. He pointed 

 out further that water can pass through the skin in either direction, 

 since when frogs, tritons, or salamanders are placed in almost dry air 

 they lose about 30 per cent, of their body-weight through the skin. 

 He quotes Overton's conclusion that the osmotic pressure of frogs 

 absorbing water, when immersed wholly or partially within it, is 



^ Weymouth Reid, Schafer's Textbook of Physiology, vol. i, p. 690. 

 2 Hober, Korânyi and Richter's "Physik. Chemie u. Medizin," vol. i., p. 342, 

 1907. 



