GENERAL BIOLOGY. 3 
alone can beget protoplasm; cell begets cell. Ommne animal. 
(anima, life) 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 composing the cell-units of which living beings are 
made are visible under the microscope; their united effects 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 will be invented, there are molecular 
movements, ceaseless as the flow of timeitself. All the processes 
which make up the life-history of organisms involve this mo- 
lecular 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 above will be illustrated in the simpler 
forms of plants and animals in the ensuing pages, and will be- 
come clearer as each chapter of this work is perused. They 
form the fundamental laws of general biology, and may be 
formulated as follows: 
1. Living matter or protoplasm is characterized by its chem- 
ical 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 zodlogy or botany, it 
tends to breadth to have a science of general biology which 
deals with the properties of things simply as living, irrespective 
very much as to whether they belong to the realm of animals 
or plants. The relation of the sciences which may be regarded 
