Action Exerted by Antagonistic Electrolytes. 109 



are held in position by additional supporting sections of tightly 

 fitting rubber tubing. Emulsion membranes of this type when 

 exposed to the influence of various antagonistic electrolytes 

 exhibit variations in electrical conductivity and permeability 

 corresponding almost exactly with those observed by Osterhout in 

 the case of laminaria under similar working conditions. For 

 example, .52 M NaCl causes a rapid rise in the conductivity of a 

 saturated filter-paper membrane until the level of the environing 

 solution is almost reached, while .278 M CaCl 2 causes first a con- 

 siderable fall in conductivity which is followed subsequently by a 

 rise to approximately the same level as in the case of NaCl. The 

 most remarkable paralleling of Osterhout's results may be obtained 

 by exposing emulsion layers or films to brief alternating treat- 

 ments with NaCl and CaCl 2 . As in the case of laminaria, alter- 

 nating variations in conductivity within comparatively wide 

 limits may be obtained without any apparent injury to the mem- 

 brane which may subsequently be returned to sea-water or a 

 balanced solution of NaCl and CaCl 2 and exposed to a similar 

 treatment the next day. However, just as in the case of laminaria, 

 too prolonged an exposure to either NaCl or CaCl 2 may cause 

 changes in electrical conductivity and permeability beyond the 

 critical point at which recovery is still possible and the mem- 

 branes subsequently exhibit extremely erratic results or fail en- 

 tirely to respond to treatment. That electrical conductivity 

 experiments on membranes of this type or living tissues afford an 

 index of their permeability to water and water-borne substances 

 was demonstrated by paralleling the above experiments in the 

 following manner: Layers of emulsion supported between filter 

 paper and rubber tubing were introduced into a series of long glass 

 tubes and the speed with which distilled water, sea-water and 

 solutions of NaCl and CaCl 2 and a balanced mixture of NaCl 

 and CaCl 2 flowed through the membrane was determined by 

 measuring the fall of the fluid in each tube at given time intervals. 

 The distilled water, sea-water and suitably balanced mixtures of 

 NaCl and CaCl 2 flowed through the membranes at approximately 

 equal speed while NaCl flowed through the membrane at a vastly 

 greater speed and CaCl 2 at a somewhat reduced speed. The 

 relative speeds of flow of various solutions were found to correspond 



