FROG. 691 



from without inwards, is directly associated with the vigour of the 

 animals, lasting seventy to eighty hours after death in strong frogs, 

 but only twenty-four hours or so in feeble animals at the end of the 

 breeding season. 



Again, the magnitude of an ordinary osmotic stream, maintained 

 through freshly removed skin by means of solutions, whose injurious 

 effect on tissue life is minimal, is capable of variation in the direction of 

 increase or decrease, by such conditions as are known to exalt or depress 

 the activity of living matter. If an osmotic current is set up in the 

 direction from without inwards through living frog's skin (the normal 

 direction of greater permeability when the skin is fresh), the presence 

 of a stimulant (alcohol) increases, while that of a depressant (chloro- 

 form) decreases the current ; on the other hand, if the osmotic current 

 has been set up in the reverse direction, i.e. from within out, the stimu- 

 lant causes diminution, and the depressant augmentation of the amount 

 of fluid transferred from the inner to the outer surface of the skin in a 

 given period of time. The phenomena failed to manifest themselves 

 when dead skin was made the subject of experiment. The same observer 1 

 was also able to demonstrate the existence of a current of -6 per cent, 

 sodium chloride solution from the outer to the inner surface of freshly- 

 removed skin, when the same solution at equal pressure was on either 

 side, and hence filtration and osmosis put out of court. 



These results are difficult to explain, and must provisionally be 

 attributed to some unknown epithelial action. 



l Brit. Med. Journ., London, 13th Feb. 1892. 



