( 164 ) 



0/i the Luminousness observed in the Eyes of' Human Beings^, 

 and also in those of Cats, Dogs, Horses, and Sheep ^ By 

 Dr Charles Ludwig Esser *. 



XjLppe A RANGES of light, as is well known, are not uncommon 

 in inferior animals, and the number of luminous animals in the 

 sea is so great, that large tracts of the water's surface have 

 been seen to be illuminated by them. 



This phenomenon, however, is comparatively seldom observ- 

 ed in fishes, and the more rarely the higher we ascend in the 

 scale of the animal kingdom, if under the denomination of lumi- 

 nousness, we understand the real evolution of light, and do not 

 consider it as the reflection of the incident rays of light ; for in 

 this latter case the luminous appearance does not inhere in the ani- 

 mal body itself, but is in reality merely a reflection, which is totally 

 different from the evolution of light in the inferior animals. A 

 real phosphorescence is sometimes observed in the higher animals, 

 and even in human beings, particularly in their excrementitious 

 fluids. The light of the eggs of the lizard, the luminousness 

 of the perspired matter in man and horses, the irradiation of 

 light in cats and other animals, from the stroking of their hair, 

 and finally the phosphorescent quaHty of human urine, have 

 been frequently observed. 



On most of these various kinds of light, I have neither per- 

 formed experiments myself, nor have I collected the facts of 

 others ; the present memoir being chiefly devoted to an exami- 

 nation of the light or luminousness of the eyes in human beings 

 and inferior animals. 



The more perfectly to accomplish this object, I some years 

 ago performed a series of experiments, that led to an important 

 result. 



Having brought a cat into a room half darkened, I observed 

 that the eyes of the animal when opposite the window, and in a 

 certain direction to myself, sparkled very brilliantly, which phe- . 

 nomenon suddenly vanished, when I, either by the motion of my ' 

 head, changed the direction of my eyes to those of the cat, or the 



• Karsten's Archiv, b. viii. heft iv. 



