REACTIONS OF NECTURUS TO STIMULI THROUGH SKIN 91 



(b) The Reactions to Alkalies and Alkaline Earth Salts 



The reactions of Necturus to alkalies are given in tables 

 XII-XV. Potassium hydroxide and ammonium hydrate did not 

 produce as definite responses as did the acids. The different 

 regions of the body varied in sensitiveness, but the gills were 

 always the most sensitive region. The reactions of the gills 

 to one per cent potassium hydroxide were greater than to ten 

 per cent nitric acid, but the other regions of the body were 

 less sensitive to potassium hydroxide or ammonium hydrate. 

 The limit of reaction for both was a 0.01 per cent solution. 



It is apparent from inspecting tables XVI-XIX that Necturus 

 is more sensitive to magnesium sulphate than to magnesium 

 chloride. The nostril region was the most sensitive to magne- 

 sium sulphate. At 0.05 per cent magnesium chloride the nostril 

 region only was sensitive, while at the same per cent Necturus 

 was sensitive to magnesium sulphate in the regions of the nos- 

 trils, head and gills. Necturus will not react to either chemical 

 at 0.01 per cent. 



TABLE XII 

 Reactions to 1% Potassium Hydroxide 



