Even the richest soil, if left uncultivated will produce the rankest weeds.
It is useful to constantly observe, note, and consider.
The grave will fall in upon him who digs it.
One day the world will look upon research upon animals as it now looks upon research on human beings.
An artist who lacks the power of self-criticism accomplishes but little. It is good if your work stands higher than your own opinion of it; bad if it is on the same level. But it is a great disaster if your work stands lower than your judgment of it.
... we might say that the earth has a spirit of growth; that its flesh is the soil, its bones the arrangement and connection of the rocks of which the mountains are composed, its cartilage the tufa, and its blood the springs of water.