84 



MARY HONORA SAYLE 



REACTIONS TO CHEMICALS 



For testing the effect of chemicals on the skin, the surface of 

 the body of Necturus was divided into seven regions, selected 

 mainly for the different responses that result from their stimu- 

 lation. They were the regions of the nostrils, head, gills, pectoral 

 girdle, pelvic girdle, back, and tail. With each solution used all 

 the regions were tested with each concentration, and the time 

 given for reaction was always the same, fifteen seconds. If no 

 response was made during the period, it was recorded as no 

 action. The location of the regions are shown in figure 1. 



i;.i..ls H««J iu» e "&Xl 



Fig. 1. Outline of Necturus maculosus, showing the regions stimulated 



in the experiments 



The substances used in the work were hydrochloric, sulphuric, 

 nitric and acetic acids; potassium hydroxide, ammonium hydrate, 

 magnesium chloride, magnesium sulphate, alcohol and clove oil. 

 In the experimental work all of these solutions were gradually 

 diluted until the limit of reaction was reached. Sufficient time 

 was given between tests at different degrees of concentration 

 and with different substances to eliminate after effects. 



The solutions were applied by means of a pipette and were 

 ejected slowly with the tip of the pipette held about two milli- 

 meters from the skin. In all cases the animal was completely 

 covered with water during the experiment. 



(a) The Reactions to Acids 



In tables I to XI are given the reactions of Necturus to the 

 four acids used. Necturus responds to acid stimuli by locomo- 

 tion or by a movement of the regions stimulated. If the acid 

 is strong, locomotion takes place; if it is weak, local response 



