I would be the last to deny that the greatest scientific pioneers belonged to an aristocracy of the spirit and were exceptionally intelligent, something that we as modest investigators will never attain, no matter how much we exert ourselves. Nevertheless ... I continue to believe that there is always room for anyone with average intelligence ... to utilize his energy and ... any man could, if he were so inclined, be the sculptor of his own brain, and that even the least gifted may, like the poorest land that has been well-cultivated and fertilized, produce an abundant harvest.

It is notorious that the desire to live increases as life itself shortens.

What a cruel irony of fate, to pair together, like Siamese twins united by the shoulders, scientific adversaries of such contrasting character!

Nothing inspires more reverence and awe in me than an old man who knows how to change his mind.

As long as our brain is a mystery, the universe, the reflection of the structure of the brain will also be a mystery.

Physical pain is easily forgotten, but a moral chagrin lasts indefinitely.

In the study of this membrane [the retina] I for the first time felt my faith in Darwinism (hypothesis of natural selection) weakened, being amazed and confounded by the supreme constructive ingenuity revealed not only in the retina and in the dioptric apparatus of the vertebrates but even in the meanest insect eye. ... I felt more profoundly than in any other subject of study the shuddering sensation of the unfathomable mystery of life.