the blood?

What is animal heat?

What is the temperature of the body?

These questions were all answered fairly well by the class, but the
answers contained only so many bits of isolated information, and the
pupils did not understand the subject after they had recited upon it.
Another teacher asked the following questions:

Why must the body have air to breathe?

Of what use is oxygen in the body?

Where does this oxidization, or burning up of worn-out
cells, take place?

But how is the oxygen carried to every part of the body and
brought into contact with the tissues?

Where do the corpuscles of the blood get their loads of
oxygen?

What gas do they give up in exchange for the oxygen?

Where do they get the carbon dioxide?

How does air entering the lungs differ from air leaving
them?

What corresponding change takes place in the blood while it
is in the lungs?

Explain how the change is effected in each case.

Suppose we breathe air that contains too little oxygen, what
will be the effect on the corpuscles?

What will be the effect on oxidization in the tissues?

And what is the effect of poor oxidization on physical
vitality?

On mental vitality?

The class that answered these questions not only had the information
belonging to each separate question, but also understood the lesson as
a whole, because each question grew out of the ones that preceded it,
thus making the recitation a unified whole.

5. _The principle of clearness_

Questions must be made clear, so that their meaning may be understood.
This is not always an easy task, and the teacher frequently misses
being wholly clear. This is evidenced by the fact that often when a
pupil fails to answer a question asked in one way, he can answer it
easily when the wording is changed. This means that the difficulty for
the pupil existed in the question, and not in the answer.

Clearness in questioning involves three factors: (1) Freedom from
ambiguity or obscurity of wording; (2) adaptation to the age and
understanding of the pupil; (3) reasonable brevity.

_a. Freedom from ambiguity or obscurity of wording._--This is
fundamentally a matter of the use of good English. It requires such a
choice and arrangement of words and clauses that there can be no doubt
as to the meaning to be conveyed. Assuming a fair command of the