l-HE DOMESTIC CAT. 305 



but in the twilight the pupil resumes its natural 

 roundness, and the animal enjo3'S perfect vision. — - 

 It appears somewhat singular, that, on plunging the 

 head of a Cat into water, although the animal be 

 exposed to a very bright light, the pupil should be- 

 come immediately expanded to all its width. This, 

 however, is to be accounted for on optical prin- 

 ciples *. 



It has been remarked, that the eyes of Cats al- 

 wayss hine with a bright light when they are in the 

 dark. The Rev. William Jones was induced to make 

 some experiments on this circumstance, from having 

 observed, among the eyes of some Sheep and Oxen 

 which he had procured for dissection, that one o£ 

 them shone in the day-time much in the same man- 

 ner as the eyes of Cats do in the dark. On examin- 

 ing into this, he found that if his hand was placed 

 between the nearest window and the extremity of 

 the optic nerve (a part of which, nearly an inch 

 long, remained with the eye, and was accidentally 

 pointed towards the window), the light immediately 

 disappeared -{-. — From this he was led to consider, 

 whether the light that appears in the eyes of some 

 animals in the night time, is really a reflection 

 of light from the eye, as is commonly supposed ; 

 or, whether it does not rather fass into the eye, through 

 the optic 7ierve, from the body of the animal? It is 

 not easy to conceive how this shining light can be 

 occasioned by a reflection of light from the bottom 



* Martyn, iii. 192. 

 t Essay on the First Principles^ of Natural Philosopliy, 



Vol. I. X 



