GENERAL BIOLOGY. 3 



Laving things alone give rise to living things ; protoplasm 

 alone can beget protoplasm ; cell begets cell. Omne animal 

 (anima, Ufe) ex ovo applies with a wide interpretation to all 

 living forms. 



From what has been said it will appear that life is a condi- 

 tion of ceaseless change. Many of the movements of the pro- 

 toplasm composiag the cell-units of which living beings are 

 made are visible under the microscope ; their united efEects are 

 open to common observation — as, for example, in the move- 

 ments of animals giving rise to locomotion we have the joint 

 result of the movements of the protoplasm composing millions 

 of muscle-cells. But, beyond the powers of any microscope that 

 has been or probably ever wiU be invented, there are molecular 

 movements, ceaseless as the flow of time itself. All the pro- 

 cesses which make up the life-history of organisms involve this 

 molecular motion. The ebb and flow of the tide may symbolize 

 the influx and efflux of the things that belong to the inanimate 

 world, into and out of the things that live. 



It follows from this essential instability in living forms that 

 life must involve a constant struggle against forces that tend 

 to destroy it ; at best this contest is maintained successfully for 

 but a few years in all the highest grades of being. So long as 

 a certain equilibrium can be maintained, so long may life con- 

 tinue and no longer. 



The truths stated a.bove will be illustrated in the simpler 

 forms of plants and animals in the ensuing pages, and will 

 become clearer as each chapter of this work is perused. They 

 form the fundamental laws of general biology, and may be for- 

 mulated as follows : 



1. Living matter or protoplasm is characterized by its chemi- 

 cal composition, being made up of carbon, hydrogen, oxygen, 

 and nitrogen, arranged into a very complex molecule. 



2. Its universal and constant waste and its repair by inter- 

 stitial formation of new matter similar to the old. 



3. Its power to give rise to new forms similar to the parent 

 ones by a process of division. 



4. Its manifestation of periodic changes constituting devel- 

 opment, decay, and death. 



Though there is little in relation to living beings which 

 may not be appropriately set down under zoology or botany, it 

 tends to breadth to have a science of general biology which 

 deals with the properties of things simply as living, irrespective 



