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 aide 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. 
1 Brit. Med. Journ., London, 13th Feb. 1892. 
