While you are experimenting, do not remain content with the surface of things.

As we have seen, bread, and especially dry bread, evokes secretion of considerably larger quantities of saliva than meat.

Do not become archivists of facts. Try to penetrate to the secret of their occurrence, persistently search for the laws which govern them.

But man has still another powerful resource: natural science with its strictly objective methods.

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.

As was to be expected, the discovery of the nervous apparatus of the salivary glands immediately impelled physiologists to seek a similar apparatus in other glands lying deeper in the digestive canal.

Learn, compare, collect the facts!