THE EVOLUTION OF MAN 



lump of animated substance. The individual 

 body in the other gjroup of animals is composed 

 of many such cells, which form a sort of co- 

 operative association with division of labor. Well 

 then, the body of man is built up with billions 

 of such cells in the most wonderful manner. 

 It consists of living building material, the cells, 

 which make up its muscles, its blood, its skin and 

 even its bones. In other words, man belongs to 

 the group of animals that contain many cells, 

 (lie does not belong to the uni-cellular low arch- 

 Ityjges/ he is not a microscopically small in- 

 ifusorium.ft 



This higher group of animals is again di- 

 vided into a number of groups, among which 

 we must make our choice. There are the sponges, 

 the polypi, the jelly-fish, the worms, the star- 

 fish, the echinoderms, the crustaceans, the in- 

 sects, the snails, the shells, and, finally, ajjrpup 

 which is distinguished by a spinal cord located 

 above the digestive tract and protected by a more 

 or less solid structure which serves at the same 

 time for the support of the body, a backbone. 

 We call this last group the vertebrates. No other 

 group has this characteristic structure, and it is 

 plain, at the first glance, that man can belong- 

 only to this group, because he has a spinal cord 



