Observations on the Chameleon. 538 



rent sets of nerves, the propagation of sensation and contrac- 

 tion on each side of a ligature tied round a nerve, as well as 

 to the curious law established by Lehot and Marianini : * as 

 to the latter, I think the physiological conditions through 

 which the circulation of the nervous currents in the chame- 

 leon is effected, with reference to each lateral half, divided 

 from the other by the perpendicular mesial plane of the bo- 

 dy, would, if known, throw much light on the general condi- 

 tions on which the limitation of the electrical currents in ani- 

 mals depend. 



The remote cause of the difference of colour in the two la- 

 teral halves of the chameleon may, in most cases, be distinctly 

 referred to the manner in which the light acts upon the ani- 

 mal. The statement of Murray, that the side turned towards 

 the light is always of a darker colour than the other, is per- 

 fectly true. This rule holds good, as well with reference to 

 the direct and diffused light of the sun or moon, as to artifi- 

 cial light. Even when the animal was moving in the walks 

 of my garden, and happened to approach near enough to the 

 border to be shaded on one side by the box edging, that side 

 would instantly become less darkly coloured than the other. 

 As however the light in these cases but seldom illumines ex- 

 actly one lateral half of the animal in a more powerful man- 

 ner than the other, whereas the mesial line is constantly the 

 line of demarcation between the two different shades of co- 

 lour, we must evidently refer the different effects to two dif- 

 ferent centres, from which the nervous currents can only radi- 

 ate, under such circumstances, towards the organs situated on 

 one side of the mesial plane respectively. 



Over these centres, without doubt, the organ of vision im- 

 mediately presides ; and indeed we ought not to wonder that 

 the action of light has such powerful effects on the highly ir- 

 ritable organism of the chameleon, considering that the eye 

 is by far the most active, and one of the most highly develop- 

 ed organs. The lungs are, under such circumstances, but se- 

 condarily affected ; but they are likewise more strongly ex- 

 cited on the darker side, which is constantly more convex 

 than the other. 



Many other circumstances may be brought forward in fa- 

 vour of the opinion that the nervous currents in one lateral 

 half of the chameleon, are going on independently of those in 

 the other ; and that the animal has two lateral centres of per- 

 ception, sensation, and motion, besides the common one, in 

 which must reside the faculty of concentration. Notwith- 



* Bibliotheque Univ. de Geneve, May, 1838. 



