Henry Ernest Dudeney/Puzzles and Curious Problems/147 - Blindness in Bats

by : $147$

 * Blindness in Bats
 * A naturalist was investigating (in a tediously long story) whether bats are in fact actually blind.
 * He discovered that blindness varied.
 * Two of his bats could see out of the right eye,
 * just three of them could see out of the left eye,
 * four could not see out of the left eye,
 * and five could not see out of the right eye.
 * He wanted to know the smallest number of bats that he could have examined in order to get these results.