at different intervals, without proportionate advancement.
The same principle applies equally to the moral and intellectual
powers, because these operate by means of material organs.

840. "According to this principle, it follows, that in learning a
language or science, six successive months of application will be more
effectual in fixing it in the mind and making it a part of its
furniture, than double or treble the time, if the lessons are
interrupted by long intervals. Hence it is a great error to begin and
study, and then break off, to finish at a later period. The fatigue
is thus doubled, and the success greatly diminished.

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Of mechanics' shops? 838. Is repetition necessary to make a durable
impression on the mind? Why? 839. How is it with physical education?
840. What follows, according to this principle?

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841. "The best way is to begin at the proper age, and to persevere
till the end is attained. This accustoms the mind to sound exertion,
and not to _fits_ of attention. Hence the evil arising from long
vacations; and also the evil of beginning studies before the age at
which they can be understood, as in teaching children the abstract
rules of grammar, to succeed in which, implies in them a power of
thinking, and an amount of general knowledge, which they do not
possess."

842. _The skull is susceptible of fractures from slight blows._ This
occurs most frequently when the blow is given on the side of the head
above and anterior to the ear. Here the bone is very thin, and often
quite brittle. For these reasons, no instructor, or any person, should
punish a child by striking upon any portion of the head.

_Observation._ A few years since, a teacher in one of the Middle
States gave a pupil a slight blow upon the head. It fractured the
skull and ruptured a blood-vessel of the brain, causing a loss of
consciousness, and finally death.

843. _Concussion of the brain may be produced by blows, or by
violently shaking a person._ As the brain is of pulpy consistence, the
atoms of which it is composed, and the circulation of blood in its
minute vessels, may be disturbed by the vibration from a blow on the
exterior of the skull-bones. This disturbance of the cerebral organ is
attended with unpleasant sensations, dizziness, loss of memory and
consciousness. These may be followed by headache and inflammation of
the brain. Concussion of the brain, and the results