“Nature is cruel; therefore we are also entitled to be cruel. When I send the flower of German youth into the steel hail of the next war without feeling the slightest regret over the precious German blood that is being spilled, should I not also have the right to eliminate millions of an inferior race that multiplies like vermin?” 

Adolf Hitler, quoted in "Hitler," by Joachim Fest, Vintage Books Edition, 1974, p. 679-680

“We have - I would say, as very consistent National Socialists, taken the question of blood as our starting point. We were the first really to solve the problem of blood by action, and in this connection, by problem of blood, we of course do not mean antisemitism. Antisemitism is exactly the same as delousing. Getting rid of lice is not a question of ideology. It is a matter of cleanliness.”

Speech by Reichsfuehrer-SS Himmler at Kharkow, April 1943. 
Nazi Conspiracy and Aggression - Washington, U.S Govt. Print. Off., 1946, Vol. IV, p. 572-574: