THE CELL AND PROTOPLASM. 59 



and philosophical study by the discoveries which 

 are grouped around the terms cells and proto- 

 plasm. Cells and protoplasm have become so 

 thoroughly a part of modern biology that we can 

 hardly picture to ourselves the vagueness of 

 knowledge before these facts were recognized. 

 Perhaps a somewhat crude comparison will illus- 

 trate the relation which the discovery of cells 

 had to the study of life. 



Imagine for a moment, some intelligent being 

 located on the moon and trying to study the phe- 

 nomena on the earth's surface. Suppose that he 

 is provided with a telescope sufficiently powerful 

 to disclose moderately large objects on the earth, 

 but not smaller ones. He would see cities in 

 various parts of the world with wide differences in 

 appearance, size, and shape. He would see rail- 

 road trains on the earth rushing to and fro. He 

 would see new cities arising and old ones increas- 

 ing in size, and we may imagine him speculating as 

 to their method of origin and the reasons why they 

 adopt this or that shape. But in spite of his most 

 acute observations and his most ingenious specu- 

 lation, he could never understand the real signifi- 

 cance of the cities, since he is not acquainted 

 with the actual living unit. Imagine now, if you 

 will, that this supramundane observer invents 

 a telescope which enables him to perceive more 

 minute objects and thus discovers human beings. 

 What a complete revolution this would make in 

 his knowledge of mundane affairs! We can 

 imagine how rapidly discovery would follow dis- 

 covery ; how it would be found that it was the 

 human beings that build the houses, construct 

 and run the railroads, and control the growth 

 of the cities according to their fancy ; and, lastly, 



