Their touch is almost senseless to a sore, and a wound generally raises no sharp pain.

The like also in their hearing may be observed; for old musicians play louder and sharper than others, that they may move their own dull tympanum with the sound.
For what steel is to the edge in a knife, that spirit is to the sense in the body; and therefore, when the spirits fail, the sense grows dull and stupid, and cannot be raised, unless by something, such as strong wine, that makes a vigorous impression.
QUESTION VIII.

WHY OLD MEN READ BEST AT A DISTANCE.
PLUTARCH, LAMPRIAS, AND OTHERS.
To my discourse in the former problem some objection may be drawn from the sense of seeing in old men; for, if they hold a book at a distance, they will read pretty well, nearer they cannot see a letter and this Aeschylus means by these verses:-- Behold from far; for near thou canst not see; A good old scribe thou mayst much sooner be.
And Sophocles more plainly:-- Old men are slow in talk, they hardly hear; Far off they see; but all are blind when near.
And therefore, if old men's organs are more obedient to strong and intense qualities, why, when they read, do they not take the reflection near at hand, but, holding the book a good way off, mix and weaken it by the intervening air, as wine by water?
Some answered, that they did not remove the book to lesson the light, but to receive more rays, and let all the space between the letters and their eyes be filled with lightsome air.

Others agreed with those that imagine the rays of vision mix with one another; for since there is a cone stretched between each eye and the object, whose point is in the eye and whose basis is the object, it is probable that for some way each cone extends apart and by itself; but, when the distance increases, they mix and make but one common light; and therefore every object appears single and not two, though it is seen by both eyes at once; for the conjunction of the cones makes these two appearances but one.

These things supposed, when old men hold the letters close to their eyes, the cones not being joined, but each apart and by itself, their sight is weak; but when they remove it farther, the two lights being mingled and increased, see better, as a man with both hands can hold that for which either singly is too weak.
But my brother Lamprias, though unacquainted with Hieronymus's notions, gave us another reason.