THE DEVELOPMENT OF A YOUNG MONKEY 123 



finger, exposing his toothless lower jaw. After sucking at the 

 finger he drew back with a frown. 



His face is not mobile but he has three easily recognized 

 expressions ; ordinarily his face is impassive, with an expression 

 of great seriousness, even melancholia; when he is satisfied or 

 interested he sucks his tongue, pursing up his lips and chewing; 

 when angry or disappointed he frowns. There is no expression 

 comparable to the human smile. 



He is quite unafraid and is attracted only by the observer's 

 movements. He is frightened by squeaking or tearing sounds, 3 

 but not by whistling or clapping. He runs about actively and 

 bites at every new object. 



August 3. Baby climbed some distance up the wire netting 

 today .. When he was 18 inches from the ground Dolly reached 

 up and pulled him down into her arms. He seems to enjoy 

 climbing up and down the edge of the window sill, a distance 

 of about four inches. 



I put a bit of bread and milk in his mouth. He sucked at it 

 but did not attempt to swallow it, finally letting it fall from his 

 mouth. 



He has learned to jump from the window ledge to the ground. 

 Previously he would put his hands to the ground before drop- 

 ping off; but now he drops boldly. 



He tastes the bread and milk that I have given Dolly, usually 

 placing his hands upon it and bending down to suck at it. Twice, 

 however, he gathered a large piece of bread up into his arms, sit- 

 ting back upon his haunches. The hands are not used well for 

 grasping. He does not try to swallow the bread, but merely 

 sucks at it. His biting seems now to be limited to light colored 

 objects, bread, paper, carrot, etc. When Dolly is feeding and 

 he approaches her she crouches down until her face is level with 

 his, stares at him for a moment, then slaps or bites him. This 

 makes him cry and she immediately draws him into position. 



August 7. He is very playful today. He stands up on his 

 hind feet, runs forward a few steps with arms outstretched, 

 and pounces upon a piece of paper or other object. He climbs 



3 Noises of this type, rustling, tearing and squeaking sounds, seem to be par- 

 ticularly terrifying to the young of animals differing widely in habit. 



