Below, a quote from Robert Lifton’s historical/psychological book, “The Nazi Doctors.”

“Under the Nazis, there was increasing discussion of the possibility of mercy killings, of the Hoche concept of the ‘mentally dead,’ and of the enormous economic drain on German society caused by the large number of these impaired people. A mathematics text asked the student to calculate how many government loans to newly married couples could be granted for the amount of money it cost the state to care for ‘the crippled, the criminal, and the insane.'”

See quote from, The Nazi Doctors: Medical Killing and the Psychology of Genocide; p.48.

Also, Euthanasia: a creeping corrosion.