Many years ago, when I was young and invulnerable, it was most amusing that Mr. Barkis, the "willin'" carrier in David Copperfield, offered up his shillings with such agony.
Barkis is bedridden with a cripplingly painful illness. He has a locked box of coins, and although he has become "near," he has the generous impulse to give David a guinea. However, to fetch the money costs him a martyrdom. "He endured unheard-of agonies in crawling out of bed alone, and taking it from that unlucky box.... We heard him uttering suppressed groans of the most dismal nature. This procedure racked him in every joint."
Barkis's pain was, once upon a time, comic. Nowadays, alas, I can only imagine that Barkis has ruptured a disc, and must endure a chronic, unameliorable, incurable torture that will only end with his death.
And then there's the Fat Boy, in Pickwick Papers, who cannot prevent himself from falling asleep. What's so funny about chronic fatigue or narcolepsy? At my present advanced age, I tend to fall asleep every time I lie down with a book, even if the book is a wild extravagant wonderful novel by Charles Dickens. Inopportune sleep by day is almost as unpleasant as insomnia or nightmares (or insomnia plus nightmares) at night.
I think also of Mr F.'s demented Aunt, in Little Dorrit , who can no longer follow the conversation, but "after regarding the company for ten minutes with a malevolent gaze,
delivered the following fearful remark:'When we lived at Henley,
Barnes's gander was stole by tinkers.'"'
Is her senility, or as we would now say, her Alzheimer's, so very amusing.
It were, but now it ain't no longer.
Dickens died young, at 58, so there is no way to know whether his sense of humor would been softened by the ravages of disease and age.