S02 M. Prevost on the shining of the Eyes of the Cat, 



or at lea^ this is subject to numerous exceptions. Besides what 

 I have said of the cat in which I certainly excited lively passions, 

 and whose eyes yet gave no sign of luminosity, it is easy to 

 prove directly that the phenomenon may take place independent- 

 ly of the passions ; for the animals whose eyes shine in the dark 

 do not lose this property with life, and are susceptible of it even 

 long after they are dead. I have seen two polecats that had been 

 dead fifteen or twenty hours, whose eyes shone nearly like those 

 of living cats. I have remarked the same thing in serpents and 

 insects. I have also seen the eyes shine in some collared snakes 

 which I extracted from the egg a considerable time before the 

 period when they would naturally have come forth. There was 

 no appearance then of their being susceptible of lively passions. 

 It may be added that the animals whose eyes shine most, are of- 

 ten very tranquil at the moment when the phenomenon is most 

 striking. 



It was not enough to consider the shining of the eyes as phos- 

 phoric ; it has also been pretended that it serves as a light to the 

 animals which possess it, and that it assists them in seeing and 

 guiding themselves in the dark. But the place which the re- 

 flectors occupy is reasonably a matter of astonishment, for it is 

 not the light which proceeds from the eye to an object that en- 

 ables the eye to perceive that object, but the light which arrives 

 in the eye from it. 



Spallanzani thought that cats, polecats, and tome other ani- 

 mals, move with promptitude and certainty in a medium totally 

 deprived of light, and this is also a subject of pretty general 

 belief. I cannot help doubting it however. But should this 

 really be the case, it ought not to be attributed to the shining of 

 their eyes, since this aid, as we have seen, fails them when they 

 have most need of it. Animals in the state of nature are never 

 placed in such circumstances. Nor is it even probable that such 

 an occurrence takes place in a state of domesticity. In whatever 

 part they may happen to be, there is always a little light, and 

 in order to see, they only require to have their pupil susceptible 

 of great dilatation, and their retina of an extreme sensibility. It 

 is said that a man shut up for a long time in a very dark dun- 

 geon becomes at length able to read. The nocturnal birds 

 which Spallanzani reared, saw very well in a place in which he 



