Roberts 



THE HUMAN HAND 



The versatility of the human hand is illustrated by the delicacy and sureness with 

 which an artist or surgeon operates, or by the variety and power of movements exe- 

 cuted by a workman 



The Enlarged Brain A third characteristic of our species is the large 

 brain, especially the forebrain (see illustration opposite). This brain is prob- 

 ably the most distinctive feature of man's whole life and history. For with 

 this organ is associated man's capacity to learn from the past and to push his 

 purposes and his plans farther and farther into the future (see table, p. 54). 



The Chin and Mouth Distinctive of the human face is the well- 

 defined chin (compare profiles in the illustration on page 52). We are 

 impressed when we see a person who has either no chin or one that is 

 exceptionally large. There is no obvious merit in this structure, although 

 it is probably related to the workings of the jaw and the mouth. The lips 

 as well as the teeth and the jaw show distinctive characteristics. These are 

 related to the fact that man is the only animal that uses articulate speech. 



Speech^ The hen can utter some twenty distinct sounds, and each one 

 has a different meaning. Other animals communicate with each other 

 through calls or cries. But in human speech there is more than a set of calls 

 and cries. Human language consists of words, each with a definite pattern 

 of sound. And these words are combined into sentences that express all 

 kinds of ideas. Unlike the crowing and growling and snarling of other ani- 

 mals, human speech can be constantly adjusted to the changing and grow- 

 ing needs of the thinking animal. If you have a new idea, you can, by means 

 of the language you have acquired, express it so that another person can 



^See Nos. 3 and 4, p. 60. 

 50 



