CHAPTER I. 



THE CELL. 



OBSERVATION and experience tell us that all tangible or material 

 things about us are either dead x>r alive ; that is, matter is either life- 

 less or living. 



The conception of life in its simplicity is limited to a few ele- 

 mentary phenomena, such as nutrition, evolution, reproduction, sen- 

 sibility, and motion. These properties taken together distinguish the 

 living from every form of lifeless substance. Combinations of these 

 simple, elementary phenomena give us every complex function of 

 our present life. If the study of life is the study of these elemen- 

 tary phenomena, it is necessary that our working force be brought 

 to their seat and home the cell. 



Everywhere there is a sharp line or division between living and 

 lifeless matter, although the two are frequently so closely allied that 

 first observations seem to show no distinctions. This is particularly 

 true of those things that are not seen with the naked eye micro- 

 scopical things. When one's attention is brought to such objects 

 as quartz, iron, the earthworm, or the dog, the distinction is very 

 evident. On the other hand, long and tireless observation and inves- 

 tigation are required to determine whether some of the bodies found 

 in water are dead or alive. And although so closely associated, 

 scientists have found that a living substance never comes of its own 

 accord from a lifeless one, but only through the influence of some 

 other living matter. For example, no vegetation springs up from the 

 soil until the seed (a form of dormant life) becomes buried in it; no 

 colony appears for the bacteriologist on the sterilized medium until 

 the surface is impregnated with the germ. 



Although the sharp distinction exists, nevertheless the two mate- 

 rials are very closely associated, as is shown by a little observation. 

 Plants and animals are kept alive and nourished by the food they 

 consume, and it consists, in the main, of lifeless matter. While in 

 the body it seems to be transformed, as it were, to a living state, and 

 it forms part of the body. After it has served the needs of the 

 economy of the plant or animal it dies, and is gotten rid of as waste- 

 matter. 



