THE LIVING STRUCTURES HI 



and reproduction. All these properties, which the multi- 

 cellular highly developed animal possesses, appear in 

 each separate cell at least in youth. There is no longer 

 any doubt about this fact and we may therefore regard it 

 as the basis of our physiological idea of the elementary 

 organisms." 



After this general description of the cells of the differ- 

 ent parts of the body, he makes the following statement 

 in reference to the brain cells: "In the protozoa in the 

 one cell plants and primitive animals, the whole organism 

 permanently consists only of a single cell. On the con- 

 trary in most animals and plants, it is only in the earliest 



FIG. 10. Three epithelial cells from the mucous membrane of the tongue. 

 HAECKEL. 



period of individual existence that the organism is a sim- 

 ple cell. It afterwards forms a cell society or more cor- 

 rectly an organized cell state. The human body is not 

 in reality a simple life unit as is at first the universally 

 current simple belief of man. It is rather an extremely 

 complex social community of innumerable microscopic 

 organisms, a colony or a state consisting of countless in- 

 dependent life units of different kinds of cells. * * * All 

 the numerous tissues of the animal body such as the en- 

 tirely dissimilar tissues of the nerves, muscles, bones, 

 outer skin, mucous skin and of other similar parts are 

 originally composed of cells, and the same is true of all 



