52 pliny's KATUEAL HISTOBT. [Book XI. 



nacin"-, sparkling, sedate, leering, askance, downcast, or lan- 

 guishing. Beyond a doubt it is in the eyes that the mind has 

 its abode : sometimes the look is ardent, sometimes fixed and 

 steady, at other times the eyes are humid, and at others, again, 

 half closed. From these it is that the tears of pity flow, and 

 when we kiss them we seem to be touching the very soul. It 

 is the eyes that weep, and from them proceed those streams 

 that moisten our cheeks as they trickle down. And what is 

 this liquid that is always so ready and in such abundance in 

 our moments of grief, and where is it kept in reserve at other 

 times ? It is by the aid of the mind that we see, by the aid 

 of the mind that we enjoy perception; while the eyes, like so 

 many vessels, as it were, receive its visual faculties and trans- 

 mit them. Hence it is that profound thought renders a man 

 blind for the time, the powers of sight being withdrawn from 

 external objects and thrown inward: so, too, in epilepsy, the 

 mind is covered with darkness, while the eyes, though open, 

 are able to see nothing. In addition to this, it is the fact 

 that hares, as well as many human beings, can sleep with 

 the eyes open, a thing which the Greeks express by the term 

 7t,opvJ3avriav. Nature has composed the eye of numerous mem- 

 branes of 'remarkable thinness, covering them with a thick coat 

 to ensure their protection against heat and cold. This coat she 

 purifies from time to time by the lachrymal humours, and she 

 has made the surface lubricous and slippery, to protect the eye 

 against the effects of a sudden shock. 



CHAP. 55. THE NATUKE OF THE PUPIL EYES WHICH DO NOT 



SHUT. 



In the midst of the cornea of the eye Nature has formed a 

 window in the pupil, the small dimensions of which do not 

 permit the sight to wander at hazard and with uncertainty, 

 but direct it as straight as though it were through a tube, 

 and at the same time ensure its avoidance of all shocks com- 

 municated by foreign bodies. The pupils are surrounded by a 

 black circle in some persons, while it is of a yellowish cast with 

 others, and azure again with others. By this happy combina- 

 tion the light is received by the eye upon the white that lies 

 around the pupil, and its reflection being thus tempered, it 

 fails to impede or confuse the sight by its harshness. So 

 complete a mirror, too, does the eye form, that the pupil, 



