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 diff'use 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. 



