Bis pueri senes

Ancient persons are twice children, or as we say, Once a man, and twice a child. Age ordinarily induces a degree of imbecility, both in the mind and body, resembling childhood. Persons in a very advanced age become feeble and impotent, their legs tremble, obliging them to support themselves with a stick; their hands shake, so that they are unable to cut their food, and at length of even carrying in to their mouths. They become toothless, and are obliged, like children, to be fed with spoon-meats; their eyes become weak, incapacitating them from reading, and their organs of hearing dull and obtuse, so that they can no longer take a part in conversation. These two sources of information being cut off, the mind, no longer solicited by the surrounding objects, or excited by the acquisition of new materials, becomes languid and inert; the traces of the knowledge it had acquired, become faint, and are at length nearly obliterated, and thus is induced a complete second childhood, «and mere oblivion, sans teeth, sans eyes, sans taste, sans every thing».
«Ubi jam validis quassatum est viribus aevi
Corpus, et obtusis cecitlerunt viribus artus,
Claudicat ingenium, delirat linguaque mensque».
LUCRET. Lib.III, lin 452.
When age prevails, And the quick vigour of each member fails, The mind's brisk powers decrease, and waste apace, And grave and reverend folly takes the place." Trans, by CREECH.