ERNST G. HUF 



213 



ary rise. Epinephrine seems to stimulate the mucous glands of the skin (40, 70). 

 After appHcation of neurohypophyseal principles, which increases net uptake of 

 water from the outside, a higher skin potential is obtained at a given rate of 

 sodium intlux. It has been concluded that, after the addition of the hormone, 

 more of the work done by the skin appears to be available for the formation of 

 the potential (8). Pretreatment of frogs, before using their skins, with a highly 

 puritied ACTH preparation changes the conditions in skin such that, for a 

 given skin voltage, less sodium chloride is taken up by the skin of treated frogs 

 than of untreated or sham-treated animals (28). No demonstrable difference in 

 active salt transport seems to exist between skin of normal and of adrenohypo- 

 physectomized frogs (^3)- 



13.4 mV \ / 14,3 mV 



Fig. 5. Development of skin po- 

 tentials in two symmetrical pieces 

 of skin of the abdominal wall of 

 Rana esculenla. Frog was poisoned 

 previous to the decapitation for 

 15 min. with bromoacetate (0.02 

 ml of a 4% sol./gm.) into the dor- 

 sal lymph sac. la: skin immedi- 

 ately exposed to Ringer's contain- 

 ing o.oi I m/1. lactate. lb: skin tirst 

 exposed to Ringer's containing 

 0.006 m/1. glucose, later to Ringer's- 

 lactate solution (15). 



120 150 



Increasing the outside concentration of sodium chloride leads to increase of 

 both intlux and outflux of sodium (70). The former, however, is increased more 

 than the latter, which is to say that net salt accumulation increases upon raising 

 the outside XaCl concentration. On the other hand, steeper gradients for NaCl 

 are generated by skin in diluted as compared to skin in normal or more concen- 

 trated Ringer's (24; fig. 6). The pH of the outside solution has little efifect on 

 Na intlux until pH is below approximately 5. Then, Na influx decreases con- 

 siderably (70). The inside of the skin is highly sensitive to pH changes, as 

 noted by Meyer and Bernfeld in their studies on the dependence of skin poten- 

 tial on the pH of the environment (51). Ussing found that low pH values give 

 low values for sodium influx and vice versa (70). This has been confirmed in 

 studies on net rates of salt uptake (24). Moderate elevation in COo tension of the 

 saline solutions on both sides of the skin reduced sodium influx, but left sodium 

 outflux practically unchanged. Skin potentials were diminished (70). Lowering 

 the temperature of the saline solutions from 25°C, in the controls, to 3°C,in the 



