The older Kurt Cobain got the more obsessed he seemed to become with the human anatomy, bodily functions and medical procedures, and references to all three were rife in his lyrics and artwork.
This original version of Aneurysm appeared on the Smells Like Teen Spirit single in 1991 and on the tour EP Hormoaning a year later, as well as on the With The Lights Out box set in 2004. While certainly good, this version somewhat lacks the intensity of this one:
Nirvana: Aneurysm (BBC Session)
A shorter, faster take recorded for the BBC's The Evening Session and was included on the Incesticide rarities compilation in 1992.
In 1996, two years after Cobain's death, the live album From The Muddy Banks Of The Wishkah came out and a version of Aneurysm (recorded in California on December 28th 1991) was released as a single.
Nirvana: Aneurysm (live in Del Mar, CA)
And just so we can hear the evolution of the song, here's an earlier live version of it, which features slighty different lyrics. A bootleg recording from the Off Ramp in Seattle on November 25th 1990.
Nirvana: Aneurysm (live in Seattle, WA)