Analogy cannot serve as proof.

Luck favors the mind that is prepared.

Every chemical substance, whether natural or artificial, falls into one of two major categories, according to the spatial characteristic of its form. The distinction is between those substances that have a plane of symmetry and those that do not. The former belong to the mineral, the latter to the living world.

These microscopic organisms form an entire world composed of species, families and varieties whose history, which has barely begun to be written, is already fertile in prospects and findings of the highest importance. The names of these organisms are very numerous and will have to be defined and in part discarded. The word microbe which has the advantage of being shorter and carrying a more general meaning, and of having been approved by my illustrious friend, M. Littré, the most competent linguist in France, is one we will adopt.

I have the faith of a Breton peasant and by the time I die I hope to have the faith of a Breton peasant's wife.

When I approach a child, he inspires in me two sentiments; tenderness for what he is, and respect for what he may become.

The Greeks bequeathed to us one of the most beautiful words in our language--the word 'enthusiasm'--en theos--a god within. The grandeur of human actions is measured by the inspiration from which they spring. Happy is he who bears a god within, and who obeys it.