Perfect as the wing of a bird may be, it will never enable the bird to fly if unsupported by the air. Facts are the air of science. Without them a man of science can never rise.

Appetite, craving for food, is a constant and powerful stimulator of the gastric glands.

Science demands from a man all his life. If you had two lives that would not be enough for you. Be passionate in your work and in your searching.

Learn, compare, collect the facts!

Learn the ABC of science before you try to ascend to its summit.

Don't become a mere recorder of facts, but try to penetrate the mystery of their origin.

The digestive canal represents a tube passing through the entire organism and communicating with the external world, i.e. as it were the external surface of the body, but turned inwards and thus hidden in the organism.