232 The Outline of Science 



thing new a restless inquisitiveness, a desire to investigate the 

 world, an unsatisfied tendency to experiment. We are approach- 

 ing the Dawn of Reason. 



There is a long gamut between the bushy-tailed, almost 

 squirrel-like marmosets and the big-brained chimpanzee. There 

 is great variety of attainment at different levels in the Simian 

 tribe. 



Keen Senses 



To begin at the beginning, it is certain that monkeys have a 

 first-class sensory equipment, especially as regards sight, hearing, 

 and touch. The axes of the two eyes are directed forwards as in 

 man, and a large section of the field of vision is common to both 

 eyes. In other words, monkeys have a more complete stereoscopic 

 vision than the rest of the mammals enjoy. They look more and 

 smell less. They can distinguish different colours, apart from 

 different degrees of brightness in the coloured objects. They are 

 quick to discriminate differences in the shapes of things, e.g. 

 boxes similar in size but different in shape, for if the prize is 

 always put in a box of the same shape they soon learn ( by associa- 

 tion) to select the profitable one. They learn to discriminate 

 cards with short words or with signs printed on them, coming 

 down when the "Yes" card is shown, remaining on their perch 

 when the card says "No." Bred to a forest life where alertness 

 is a life-or-death quality, they are quick to respond to a sudden 

 movement or to pick out some new feature in their surroundings. 

 And what is true of vision holds also for hearing. 



Power of Manipulation 



Another quality which separates monkeys very markedly 

 from ordinary mammals is their manipulative expertness, the co- 



