Observations on the Chameleon. 535 



thought was a slight electrical shock, when touching my cha- 

 meleon with the forefinger and thumb applied to the oppo- 

 site halves of the animal. On such occasions I have felt a 

 slight thrilling sensation, which struck me sufficiently to cause 

 me to invite M. Soret, of Geneva, who was then at Weimar, 

 and provided with the proper instruments, to submit the cha- 

 meleon to the test of the galvanometer. He had, however, so 

 little confidence in the success of the experiment, that I would 

 not have urged the point, had I not been much more confi- 

 dent myself. 



I think it not unlikely that the nervous currents may di- 

 rectly co-operate in effecting the changes of colour in the 

 chameleon, or such tissues of other animals as are subject to 

 discoloration from various affections. The experiments of 

 M. Matteucci show that such changes may be effected by the 

 animal electricity, on the accession of certain chemical sub- 

 stances, and we need only suppose that such substances are 

 mixed with the juices of the chameleon, (one of them, oxy- 

 gen, certainly is so), and that these juices are instrumental in 

 completing the electrical circle, in order to account more fully 

 for the phenomenon in question. 



My own observations on these changes all tend to prove 

 that they depend altogether on the degree in which the nerv- 

 ous system is stimulated or inactive. This principle is call- 

 ed into operation by more remote causes, as heat, light, and 

 mental affections ; and is instrumental in creating other and 

 more immediate causes, as by causing the cutaneous tissues 

 to become filled with gaseous and liquid fluids, or by effec- 

 ting the possible chemical actions and reactions which may 

 take place in various ways, under the influence of the nervous 

 currents, according to their intensity or quantity. 



According to this view, I cannot but doubt the universality 

 of the principle on which Mr. Milne-Edwards has lately tried 

 to explain all the changes of colour in the Chameleon, by 

 showing that there exist in the skin of this creature two lay- 

 ers of membranous pigment placed the one above the other, 

 but arranged in such a way as to appear simultaneously un- 

 der the scarf skin, and sometimes so that the one may con- 

 ceal the other, and by assuming that every thing remarkable 

 in the changes of colour may be explained by the appearance 

 of the pigment of the deeper ( violet or blackish-red ) layer, 

 to an extent more or less considerable, in the midst of the 

 pigment of the superficial (greyish, or more or less yellowish 

 or white) layer, or from its disappearance underneath that 

 layer. ('Edinb. New Philos. Journal,' July— Oct., 1834). 



