True friends visit us in prosperity only when invited, but in adversity they come without invitation.

Our costliest expenditure is time.

An orator without judgment is a horse without a bridle.

Alcmaeon was the first to define the difference between man and animals, saying that man differs from the latter in the fact that he alone has the power of understanding.

We must consider the distinctive characters and the general nature of plants from the point of view of their morphology , their behavior under external conditions, their mode of generation, and the whole course of their life.

Waste of time is the most extravagant and costly of all expenses.

Love is the affection of a mind that has nothing better to engage it.