Does it work like in this cartoon or only overall?
It is certainly not going to be like that for a disembodied hand, given that there are no muscles in the hand to go into rigor.
But once a muscle is in rigor, it will stay that way until decomp starts.
Si
No muscles in the hand? What edition of Gray’s Anatomy are you looking at?
Fair enough, but most of the hand (particularly gripping for the fingers) is activated from muscles in the forearm via tendon bundles.
So a hand separated from the forearm will probably have very little actual grip due to rigor in the fingers. Of course, I have never played with a detached hand, so maybe someone who has would like to comment… (although I have heard that you can flex the fingers by pulling on the tendons, but I cannot remember who told me that)
Si
The phenomenon you’re asking about is rigor mortis, not just rigor.
Thank you. I thought this thread was going to be about ensuring that mathematical proofs were sufficiently detailed. 
Yes – the OP’s question-writing lacks sufficient rigor.
It lacked mortis, actually.
And while I’ve played with a detached hand before, it’s not been a recently deceased one, so I can’t comment definitively.
I saw this and had to check.
Merriam-Webster says:
* Main Entry: rig·or
* Pronunciation: \ˈri-gər\
* Function: noun
* Etymology: Middle English rigour, from Anglo-French, from Latin rigor, literally, stiffness, from rigēre to be stiff
* Date: 14th century
1 a (1) : harsh inflexibility ,
:
:
5 a obsolete : rigidity, stiffness b : rigidness or torpor of organs or tissue that prevents response to stimuli c : rigor mortis
And then rigor mortis as a term didn’t appear until 1847.
Since Gray’s Anatomy appeared soon after in 1858, it’s possible he used the older term. A good thing for somebody to look up, other than myself.
The process of rigor mortis begins 2-6 hours after death and reaches it’s peak (stiffness) about 8-12 hours after death.
The body becomes limp again 24-84 hours after death.
This all depends on temperature and circumstances, but basically a corpse is totally limp, then gradually gets stiff, then limp again (and starts real composition) all during the first 1-3 days.
Sometimes rigor mortis doesn’t happen at all, for unknown reasons.
I don’t get the cartoon. What is the shady guy in the alley selling (aside from a severed human hand)?
He’s selling the object (PDA, maybe?) stuck in the dead hand.
As a person who holds a graduate mathematics degree, I thought the exact same thing, and I wondered whether the cartoon would be Science Cartoons Plus -- The Cartoons of S. Harris
And the linked cartoon in the OP was a dead link for me.