THE MAMMOTH CAVE. 139 
eye of the animal, gradually accustomed to light, 
finally becomes adapted to the new medium, and 
manifests the ability of exercising the sense of 
sight. This being the fact, it is to be inferred 
that the organs of vision were originally in a 
perfect condition, and afterward adapted to the 
state of darkness in which the animal existed; 
which may be conjectured to be a transitory state 
to a total obliteration of the visual organs, as has 
been accomplished in the fishes. 
Professor Silliman continues: 
“By keeping them [the rats], however, in 
captivity, and in diffuse light, they gradually 
appeared to attain some power of vision. They 
feed on apples and bread, and will not at present 
[soon after capturing them] touch animal food. 
There is no evidence that the Cave rats ever 
visit the upper air, and there was no one who 
could tell me whether they were or were not 
found there by the persons who first entered this 
place in 1802." 
‘“‘ Bats are numerous in the avenues within a 
mile or two of the mouth of the Cave, and Mr. 
Mantell thinks he has secured at least two spe- 
cies. Several specimens are preserved in alco- 
* As before stated, the Cave was not discovered until 1809. 
