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 life- 

 less matter are everywhere totally distinct, though often closely 

 associated. The most careful studies have on the whole ren- 

 dered the distinction more clear and striking, and have demon- 

 strated that living matter never arises spontaneously from lifeless 

 matter, but only through the immediate influence of living mat- 

 ter already existing. And so, whatever may have been the case 

 at an earlier period of the earth's history, we are at present justi- 

 fied in re^ardino; the line between living; and lifeless matter as 



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one of the most clearly defined and remarkable of natural boun- 

 daries. 



The contrast between living matter and lifeless matter is made 



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the ground for a division of the natural sciences into two corre- 

 sponding groups, viz.: the Biological Sciences and the Abiological 

 Sciences, dealing with living matter and lifeless matter respec- 

 tively. The biological sciences (p. 7) are known collectively as 

 Biology (fiios, life ; Xoyoz, a discourse], which is therefore often 

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

 ter. But living matter, as will shortly appear, is only ordinary 

 matter which has entered into a peculiar state or condition. 

 And hence biology is more precisely defined as the science which 

 treats of matter in the living state. 



The Relationship between Living and Lifeless Matter. 

 Although living matter and lifeless matter present this remark- 

 able contrast to one another, they are most intimately related, as 

 a moment's reflection will show. The living substance of the 

 human body, or o any animal or plant, is only the transformed 

 lifeless matter of the food which has been taken into the body 



