52 THE INVISIBLE WORLD 



plants, and millions of animals, are unicellular, 

 and, as microbes, move freely about at will. 



All cells, like all microbes, in their life processes 

 develop certain chemical products. The most of 

 these products, like most of the products developed 

 by microbes, are wholesome. All the nutritious 

 juices of animal foods are produced, or, at least, 

 enriched and flavored, by the cells of the animal. 

 So all the nourishing qualities of vegetables, grains 

 and fruits which help form a wholesome diet, are 

 produced by plant cells. 



But some cells, like some microbes, manufacture 

 poisons. As the poisons which cause all the con- 

 tagious and infectious diseases are created by cer- 

 tain microbes, so the poisons of the tarantula and 

 other insects, of the rattlesnake and other reptiles, 

 are created by the cells of these animals ; and like- 

 wise the poisons of the ivy, the nettle, the sumach, 

 and other herbs, are generated by the cells of those 

 plants. 



Like microbes, cells eat without a mouth, digest 

 without a stomach, feel without a nervous system, 

 propagate without sexual organs, and move, some 

 with, and some without, organs of locomotion. 



The cell too, like the microbe, but in a higher 

 degree, forms itself into communities, and each 

 community acts with a special purpose in view, 

 and also with a general and higher purpose shared 

 by the whole. 



Individuals of some one species of microbe, 

 and of one species only, form a colony by them- 



