fable: the old dog and his master

Another fable from Aesop that I had never seen before, and one with a particularly bittersweet lesson for those of us watching our dogs grow old.  I've left it in the older English of the source.
* * *
Men ought not to dispraise the ancient, nor to put them backe, for if thou be young, thou oughtest to desire greatly to come to be old, also thou oughtest to praise the acts or deeds, which they have done in their young age, whereof Aesop rehearseth to us such a fable. There was a Lord which had a dog, the which in his youth had beene of good kind: as namely to chase and hunt, and to have great lust to run and take the wild beasts. And when this dogge was come to old age, and that he could no more run, it hapned once that he let goe and escaped from him a Hare, wherefore his Master was wroth and angry, and in great rage began to beat him. Then said the Dogge unto him, My Master, for good service thou yeeldest me evil: for in my young age and prosperity, I served thee right well, and now that I am come to my old age, thou hatest and setteth me backe. Remember, I pray thee how that in my young age I was strong and lustie, and now when I am old and feeble, thou settest nothing by me. Therefore, who so doth any good in his youth, in his old age he shall not continue in the vertues which he possessed in his youth.

 -- from Bicknell, Ethel E. Praise of the Dog: an Anthology. London: G. Richards, 1902. pp. 33-34.