REACTIONS OF NECTURUS TO STIMULI THROUGH SKIN 83 



portion was stimulated, there was a forward movement of two 

 or three inches. The nostrils, gills, and tail were the most sen- 

 sitive regions. Stimulation with a glass rod induced similar 

 reactions as were noted for wood. Stimulation with a soft 

 brush, however, induced no locomotion. The tail and feet were 

 drawn close to the body when stimulated; the gills closed, and 

 when the nostrils were touched with the brush, there was at first 

 a backward jerk, but further stimulation produced no reaction. 



In stimulating the ventral side of the body, the mouth region 

 and the tip of the tail were found to be most sensitive. When 

 either of these regions was touched, locomotion followed, but the 

 response was slow. The gills and feet upon stimulation were 

 drawn close to the body. No other regions of the ventral side 

 were sensitive. 



Experiments were next performed to ascertain if the nerve 

 endings fatigued by chemical stimuli would react to tactile stim- 

 uli. Necturus was stimulated over its entire body with ten 

 per cent hydrochloric acid until it ceased to respond. A blunt 

 point was then used to induce tactile response, but very little 

 reaction followed. The same experiment was tried after sul- 

 phuric and nitric acid of the same strength. It was found that 

 there was more response to tactile stimulation after Necturus 

 was fatigued by hydrochloric than after sulphuric or nitric acids. 



In performing the touch experiments several points worthy 

 of note were observed: 



1. Necturus is nowhere as sensitive to a blunt as to a sharp 

 instrument. 



2. When the mouth region was stimulated the head was 

 jerked backward. 



3. The regions of greatest sensitiveness are the nostril region, 

 gills and tail. 



*4. When the gills were touched their movement ceased, but 

 when the wood, glass or brush was removed their motion went 

 on at an increased rate. 



5. When the tail was stimulated it was curled up. It was 

 most sensitive at the tip. 



6. When the hind legs were stimulated they were drawn back- 

 ward under the body, while the front legs started to walk. 



7. The dorsal region between the legs was the least sensitive 

 of all. 



