A CHAMELEON-LIKE CHANGE IN DIEMVCTYLUS. 169 



But it is a remarkable fact that in this blind condition the 

 animals are even more than normally sensitive to changes in 

 temperature. If the temperature on the water be raised by any 

 considerable amount the color of the animal changes correspond- 

 ingly, becoming much lighter. On the other hand if the tem- 

 perature of the water be lowered they again resume the intense 

 dark color which came on as the result of the operation. These 

 changes in color usually occupy a time of not far from two hours. 



The question now arose as to how this color change was con- 

 trolled. It was at first thought that it must be controlled through 

 the central nervous system, but the following experiments seem 

 to throw doubt upon such an explanation. 



Section of tlie Spinal Cord. It has been shown above that 

 section of the optic nerves brings about a most remarkable result 

 in the coloration of the salamander. Now if the impulses effective 

 in bringing about this change pass to the skin through the brain 

 and spinal cord we should find upon section of the spinal cord 

 that the parts of the skin supplied by nerves arising from the 

 spinal cord below the cut should respond in a different way from 

 those parts of the skin supplied by nerves arising from the spinal 

 cord above the cut. In order to test this possibility a number 

 of salamanders were operated upon in the following way. The 

 spinal cord was completely sectioned at the level of the third or 

 fourth thoracic vertebra while under the influence of ether. At 

 the same time other individuals were subjected to the same 

 anesthetic for the same length of time to assure us that any 

 change in the appearance of the animal was not due merely to 

 the effect of the ether. After the animals had been given oppor- 

 tunity to recover from the shock effects of the operation, no 

 change being found in the color of the skin as the result of the 



o o 



first operation, they were again taken and subjected to section of 

 the optic nerves. Following this operation, usually within a 

 period of not more than two hours there was found that same 

 remarkable darkening of the skin which has already been 

 described. And this darkening of the skin involved the whole 

 dorsal surface of the animal and not merely that part of the skin 

 controlled by nerves arising either above or below the section of 

 the spinal cord. From this it is seen that the nervous impulses 



