GENERAL BIOLOGY. 



CHAPTER I. 

 INTRODUCTORY. 



WE know from common experience that all material things 

 are either dead or alive, or, more accurately, that all matter is 

 either lifeless or living ; and so far as we know, life exists only 

 as a manifestation of living matter. Living matter and lifeless 

 matter are everywhere totally distinct, though often closely as- 

 sociated. The most careful studies have on the whole rendered 

 the distinction more clear and striking, and have demonstrated 

 that living matter never arises spontaneously from lifeless matter, 

 but only through the immediate influence of living matter already 

 existing. And so, whatever may have been the case at an earlier 

 period of the earth's history, we are justified in regarding the 

 present line between living and lifeless as one of the most 

 clearly defined and important of natural boundaries. 



The Contrast between Living Matter and Lifeless Matter is made 

 the ground for a division of the natural sciences into two great 

 groups, viz. : the Biological Sciences and the Physical Sciences, 

 dealing respectively with living matter and lifeless matter. The 

 biological sciences (p. 7) are known collectively as Biology 

 (/?z'os, life; Ao^o?, a discourse), which is therefore often de- 

 fined as the science of life, or of living things, or of living mat- 

 ter. But living matter, so far as we know, is only ordinary 

 matter which has entered into a peculiar state or condition. 



