THE LIVING MACHINE BUILDING FACTORS. 157 



and greater. Group after group of 'cells were 

 set apart for one special duty after another, and 

 the result was a larger and ever more compli- 

 cated mass of cells, with a greater and greater 

 differentiation among them. In this building of 

 the machine there was no time 

 when the machine was not 

 active. At all points the 

 machine was alive and func- 

 tional, but each step made the 

 total function of the machine 

 a little more accurately per- 

 formed, and hence raised 

 somewhat the totality of life 

 powers. This parcelling out 

 of the different duties of life 

 to groups of cells continued 

 age after age, each step being 

 a little advance over the last, 

 until the result has been the 

 living machine as we know 

 it in its highest form, with its numerous organs, 

 all interrelated in such a way as to form a 

 harmoniously acting whole. 



But a second principle in this growth of the 

 machine was needed to produce the variety which 

 is found in nature. As the different cells in the 

 multicellular mass became associated into groups 

 for different duties, the method of such division 

 of labour was not alike in all machines. A city 

 in China and one in England are alike made up 

 of individuals, and the fundamental needs of the 

 Chinaman and the Englishman are alike. But 

 differences in industrial and political conditions 



ertj 



FIG. 46. 



later step in machine 

 building in which the 

 outer cells have ac- 

 quired different form 

 and function from the 

 inner cells : ec, the 

 outer cells,whose duties 

 are protective ; en, the 

 inner cells engaged in 

 digesting food. 



