Shkldon, Rractious to Clu'iiiirnl Sfiiiuili. 289 



(»!" Wiilci-. The lu'ud is sensitive to elieiiiical sliinuli after the opera- 

 tion as before. 



Scdioti of lite Spinal Cord. — The cut was made about two centi- 

 meters eeplialad of the first dorsal fin. After the operation the fishes 

 lived for weeks, differing' from the normal individuals in their ordi- 

 nary actions only in the fact that the caudal part of the body kept up 

 a constant swinnning. The fish would be propelled to the side of the 

 tank, where it would remain for hours keeping up a vigorous swim- 

 ming movement of all the body caudad of the cut. This was never 

 observed to cease until the death of the animal. Bethe ('99) noted 

 this same swimming after section of the cord in the dogfish, but found 

 that there were intervals of cessation. When this fish was tested with 

 the solutions used on the normal fish, it was found that the caudal part 

 of the body was more sensitive than before. The reactions take place 

 from a fraction of a second to a few seconds quicker than before, 

 the reactions seemed more positive and definite and some of the fishes 

 studied reacted to slightly weaker solution. The reactions of the head 

 were practically normal. After most of the operations many of the 

 fishes failed to react to quite so weak a solution as before, due, prob- 

 ably, to the shock of the operation or to diminished vitality. The 

 reactions of the spinal fish are almost never long continued after 

 stimulation with salts or picric acid, contrary to the condition in the 

 normal animal. 



Several points are involved in these experiments. These are, how 

 does the spinal fish difter from the normal and why ? Is the observed 

 difference due to a lack of inhibition by the brain, the use of the new 

 paths for the refiexes, or stimulation of the cut ends at the cephalic 

 end of the cord? Taking up the first: Danilewski ('92) on Aniphi- 

 oxus found that "voluntary" movements ceased with removal of the 

 rostral part, the only action recorded taking place in response to 

 definite stimuli. Tie coiududed that the centers for movement lie in 

 tlie rostral part of the animal. Steiner ('88) worked on the lamprey, 

 selachians, ganoids, and teleosts. In the lamprey he found no volun- 

 tary movement of the caudal part after section^ while the other fishes 

 acted about as usual after section of the; cord except for the dead 

 weight of the head. Steiner believed that the centers for equilibrium 



