to two-thirds.

(3) The output of carbonic acid is diminished by the same amount.

(4) The bodily temperature falls.

(5) The acidity of the cortex of the brain disappears.

(6) Reflex action persists; the knee jerk is diminished, pointing to
relaxation in tone of the muscles; consciousness is suspended.

Analyzing more closely the conditions of the central nervous system,
it becomes evident that, in sleep, consciousness alone is in abeyance.
The nerves and the special senses continue to transmit impulses and to
produce reflex movements. If a blanket, sufficiently heavy to impede
respiration, be placed upon the face of a sleeping person, we know
that it will be immediately pushed away. More than this, complicated
movements can be carried out; the postilion can sleep on horseback;
the punkah-wallah may work his punkah and at the same time enjoy a
slumber; a weary mother may sleep, and yet automatically rock her
infant's cradle. Turning to the histories of sleep walkers, we find it
recorded that, during sleep, they perform such feats as climbing
slanting roofs or walking across dangerous narrow ledges and bridges.
The writer knew of the case of a lad who, when locked in his room at
night to prevent his wandering in his sleep, climbed a partition eight
to ten feet in height which separated his sleeping compartment from
the next, and this without waking.

The brain can carry out not only such complicated acts as these, but
it has been found to maintain during sleep its normal inhibitory