392 THE POPULAR SCIENCE MONTHLY. 



two nerves running close to tlie vertebral colmmn the sympa- 

 thetic nerves. Pouchet cut the spinal cord close to the brain, yet 

 the chromatophores still responded to light impression, showing 

 that they did not receive the message through the cord and spinal 

 nerves. He then divided the sympathetic nerves, and the chro- 

 matophores at once lost their power of contraction. Thus he 

 proved that the sympathetic nerves were the transmitters of the 

 optical message and not the cord. This discovery of Pouchet is, 

 psychologically, of the greatest importance, though he failed to 

 recognize it as such. He was satisfied with its anatomical and 

 physiological importance. When we remember that the action 

 of the sympathetic nerve is almost if not entirely reflex in char- 

 acter, we can see at once the psychological importance of this dis- 

 covery. This fact makes the phenomenon of tinctumutation an 

 involuntary act on the part of the animal possessing the chro- 

 matic function, and thus keeps inviolate the fundamental laws of 

 evolution, which, were the facts otherwise, would be broken. By 

 a series of experiments on newts and frogs I have confirmed the 

 conclusions of Pouchet in toto. I have gone still further in dem- 

 onstrating the fact that the sympathetic nerves are the conductors 

 of the optical stimulus. Atropia, to a certain extent, paralyzes 

 the sympathetic. Injections of this drug beneath the skin of a 

 frog render the division of the sympathetic unnecessary. The 

 chromatophores will not respond to light impression if the ani- 

 mal be placed under the influence of atropine. 



A large number of the lower animals possess the chromatic 

 function. Several years ago I placed in a large cistern several 

 specimens of the gilt catfish. This is a pond fish and is quite 

 abundant throughout the middle States. It is of a beautiful 

 golden yellow color on the belly and sides, shading into a lus- 

 trous greenish yellow on the back and head. Several months 

 after these fish had been placed in the cistern it became neces- 

 sary to clean it, and the fish were taken out. They were of a 

 dirty drab color when taken out, but soon regained their vivid 

 tints when placed in a white vessel containing clear water. They 

 had evidently changed color in order to harmonize with the black 

 walls and bottom of the cistern. Some katydids are marked tinc- 

 tumutants. I took one from the dark foliage of an elm tree and 

 placed her on the lighter colored foliage of a locust. She could 

 be easily seen when first placed on the locust. In a few moments, 

 however, she had faded to such an extent that she was scarcely 

 noticeable. I have observed that hte larvcE of certain moths, 

 beetles, and butterflies also possess the chromatic function. The 

 chromatophores in the larva of Vanessa are quite abundant, and 

 this grub is a remarkably successful tinctumutant. The power 

 of changing color so as to resemble, in coloring, surrounding ob- 



