I really see no harm which can come of giving our children a little knowledge of physiology. . . . The instruction must be real, based upon observation, eked out by good explanatory diagrams and models, and conveyed by a teacher whose own knowledge has been acquired by a study of the facts; and not the mere catechismal parrot-work which too often usurps the place of elementary teaching.
Knowing something for oneself or for communication to an expert colleague is not the same as knowing it for explanation to a student.