We achieve more than we know. We know more than we understand. We understand more than we can explain.

Well-observed facts, though brought to light by passing theories, will never die; they are the material on which alone the house of science will at last be built.

Mediocre men often have the most acquired knowledge

We must keep our freedom of mind, ... and must believe that in nature what is absurd, according to our theories, is not always impossible.

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.

The joy of discovery is certainly the liveliest that the mind of man can ever feel.

In the patient who succumbed, the cause of death was evidently something which was not found in the patient who recovered; this something we must determine, and then we can act on the phenomena or recognize and foresee them accurately. But not by statistics shall we succeed in this; never have statistics taught anything, and never can they teach anything about the nature of the phenomenon.