Karger studied various phases of sleep in children, with special reference to activity during sleep. He employed an apparatus registering movements of the child, the apparatus being attached to the bed. In order to make a record of all movements of the child, he put one foot of the bed on a piece of rubber, 2 cm. in height, the child being unaware of the experiment.
The resulting record he terms "aktogramm." He studied about 300 children, varying in age from 2½ to 12½ years. He aimed to study normal children, but none of his children were entirely normal, as all of them suffered from some disturbance for which they were brought to the hospital.
He found that in addition to variations in depth, sleep manifests variations due to movement or activity of the child, the sleep, however, being uninterrupted during this activity. He found also that the activity during