538 BIOLOGY AND HUMAN LIFE 



ways the human machine is decidedly inferior to other organ- 

 isms. For example, man's skin is much more tender than that 

 of any other animal of his size, and the hairy covering is not 

 a great protection from unfavorable weather. When it comes 

 to fighting, his nails are far inferior to cat's claws, let us say ; 

 and his teeth, which he does indeed sometimes use, are not 

 nearly so formidable as are those of many smaller animals. 

 His muscular development too is rather inferior when it comes 

 to wrestling with a non-human enemy ; and when it comes to 

 running away or to catching his prey, many of the inhabitants 

 of the forest are much swifter. 



Man has a very good eye compared to other animals, and a 

 pretty good ear, though not one of the best for discovering faint 

 sounds; but his smelling ability is of rather low rank. These 

 three senses, which are so valuable to animals in helping them 

 discover their enemies or their food at a distance, are of great 

 help to man also; but on the whole he has no advantage in 

 competition with other inhabitants of the forest. 



In spite of these various shortcomings man has contrived to 

 hold his own, and some branches of the species have become vir- 

 tually masters of their environment, through the use of the brain. 

 With this brain man has made up for his thin skin by borrowing 

 the skins of other animals and by devising substitutes for skins 

 out of other materials. He has strengthened his arms by means 

 of sticks and stones, and has lengthened his legs (that is, in- 

 creased his speed) by means of iron and brass. He has extended 

 the reach of his eyesight millions of miles beyond the surface 

 of the earth, and has seen into the world of the little— a thing 

 no other backboned animal has ever done. He can hear the 

 footsteps of a fly, and he has caught vibrations through miles of 

 space. In every direction man has made up for his organic 

 insufficiency by using the thinking organ to guide his hand. 



The struggle of man to control his natural environment has 

 succeeded largely because of the use of intelligence far in ex- 

 cess of that shown by any other species of living thing. A part 

 of his strength has come from the tendency to form groups, with 



