The nights seem to me too long... I am often scolded by Madame Pasteur, but I tell her I shall lead her to fame.

Worship the spirit of criticism. If reduced to itself it is not an awakener of ideas or a stimulant to great things, but, without it, everything is fallible; it always has the last word.

Work usually follows will.

Never will the doctrine of spontaneous generation recover from the mortal blow struck by this simple experiment.

Imagination should give wings to our thoughts but we always need decisive experimental proof, and when the moment comes to draw conclusions and to interpret the gathered observations, imagination must be checked and documented by the factual results of the experiment.

Bernard was right. The germ is nothing, the terrain is everything.

The greatest malfunction of spirit is to believe things.