THE PHYSIOLOGY OF SLEEP. 



241 



Fig. 107. Curve of intensity of sleep according to Mdnninghoff and Piesbergen. The 

 figures along the abscissa represent time in hours from the beginning of sleep ; those along 

 the ordinate the relative intensity of sleep measured in milligram-millimeters, expressing 

 the intensity of sound of a falling body necessary to awaken the sleeper. 



Fig. 108. Curve of intensity of sleep in a child of three years and eight months, as deter- 

 mined by Czerny. 



16 



