288 "Journal of Comparative Neurology and Psychology. 



for all aquatic vertebrates, due probably to the fact that sweet sub- 

 stances are substantially unknown to aquatic life. To saccharine or 

 benzylsulphonic amide very quick and definite reactions were always 

 secured. Thinking that this reaction was probably due to the acid 

 radical, the saccharine was neutralized by sodium carbonate, the re- 

 sulting product l)eing as sweet to man as is the saccharine. No re- 

 actions at all wei-e then secured, proving that those first obtained were 

 due to the acid radical. 



Comparing different regions of the body as to sensitiveness, it will 

 be noted that the head is least sensitive, Avhile the mouth, nostrils, 

 paired fins, particularly the pelvic, the anal and dorsal, especially 

 the second dorsal, are more sensitive. Areas of skin closely asso- 

 ciated with the dorsal and anal finlets are included with these fins. 



OrERATIONS. 



Some operations were next performed to find out what part of the 

 nervous system takes part in these responses. After operations no 

 fishes were subjected to experimentation until at least twenty-four 

 hours had elapsed. I^arcotization was accomi:)lished by a mixture 

 of ether and water from the effects of which the animals did not ap- 

 pear to suffer in any way. 



Destruciion of the Spinal Cord. — In this experiment the tail was 

 cut off", the caudal artery and vein plugged with cotton and the cord 

 entirely destroyed as far cephalad as the cephalic margin of the first 

 dorsal fin by means of a small steel wire. This method was suggested 

 to me by Dr. Parker, who had used it with much success. By this 

 operation the peripheral innervation of all of the caudal part and 

 middle of the body is destroyed, except that from the lateral line 

 nerve. The individuals subjected to this operation lie in the water 

 perfectly motionless so fai- as the caudal part of the body is eoucerned, 

 occasionally trying feebly to swim by meaus of the })ectoral fins. The 

 skin caudally gradually turned white as is the case with dead dogfish. 

 Such fishes ]i\'ed, however, for some weeks. As was to be expected, 

 no reactions could be obtained chemically either by stimulation of 

 the general body surface or the lateral line. Parker ('05) showed that 

 the function of the lateral line is to respond to slow mass movements 



