IT ON ANIMAL LIFE 91 
facet as an independent eye, in which case 
many insects realise the epigram of Plato — 
Thou lookest on the stars, my love, 
Ah, would that I could be 
Yon starry skies with thousand eyes, 
That I might look on thee! 
Even so, therefore, we only substitute one 
difficulty for another. 
But this is not all. We have not only no 
proof that animals are confined to our five 
senses, but there are strong reasons for believ- 
ing that this is not the case. 
In the first place, many animals have 
organs which from their position, structure, 
and rich supply of nerves, are evidently 
organs of sense; and yet which do not 
appear to be adapted to any one of our five 
senses. 
As already mentioned, the limits of hearing 
are reached when about 35,000 vibrations 
of the air strike on the drums of our ears. 
Light, as was first conclusively demonstrated 
by our great countryman Young, is the 1m- 
pression produced by vibration of the ether 
