Human diversity makes tolerance more than a virtue; it makes it a requirement for survival.

Men are naturally most impressed by diseases which have obvious manifestations, yet some of their worst enemies creep on them unobtrusively.

Biologically, man is still the great amateur of the animal kingdom; he is unique in his lack of anatomical and physiological specialization.

Sometimes the more measurable drives out the most important.

Life is short, the art is long, the problems pressing.

Eradication of microbial disease is a will-o'-the-wisp; pursuing it leads into a morass of hazy biological concepts and half truths.

Man could escape danger only by renouncing adventure, by abandoning that which has given to the human condition its unique character and genius among the rest of living things.