written by Isaac Asimov
published in 1967
A short story
Set in the Foundation universe
The story depicts a future where robotic prosthetics for humans and artificially-created organic body-parts for robots (known as Metallos) are commonplace. Metallos have been granted equal status with 'normal' humans.
A man, who has been granted the right to long life (possibly immortality) by an official Board of Mortality, meets the surgeon who is to assist in the performance of heart replacement surgery on the man. The surgeon offers him a choice between a metallic or semi-organic heart. The man stubbornly refuses the doctor's attempts to persuade him to accept an organic heart, saying that it's "weak," as compared to the cyber-heart.
Later, the surgeon remarks to a medical engineer that he would rather that humans and robots stick to being what they are instead of becoming similar. The engineer calls such talk "segregationist," to which the surgeon replies that he "doesn't care." At the end of the story, the surgeon is revealed to be a robot himself.