The physiologist is not a man of the world, he is a scientist, a man caught and absorbed by a scientific idea that he pursues; he no longer hears the cries of the animals, no longer sees the flowing blood, he sees only his idea: organisms that hide from him problems that he wants to discover. He doesn't feel that he is in a horrible carnage; under the influence of a scientific idea, he pursues with delight a nervous filament inside stinking and livid flesh that for any other person would be an object of disgust and horror.

Those who do not know the torment of the unknown cannot have the joy of discovery.

Art is 'I'; science is 'we'.

The terrain is everything; the germ is nothing.

True science teaches us to doubt and, in ignorance, to refrain.

First causes are outside the realm of science.

The fact that knowledge endlessly recedes as the investigator is about to grasp it is what constitutes at the same time his torment and happiness.