678 The Outline of Science 



It is safe to say that every organism living to-day has de- 

 scended from a pre-existing organism ; the chain of life has been 

 unbroken since before the first records of geological history 

 millions and millions of years ago. 



2 



Protoplasm and the Construction of the Body 



Protoplasm, as a great nineteenth-century biologist said, is 

 "the physical basis of life." It is the living part of all organisms, 

 whether animals or plants, as distinguished from such non-living 

 substances as hair, or the hard parts of bone, or accumulations of 

 fat or starch, all of which are products of its activity. Under the 

 microscope it is seen to be a semi-liquid substance, somewhat 

 granular, almost colourless, apparently simple, but really, as we 

 know, of the utmost chemical complexity. Some of the lowest 

 forms of life, like the Amoeba, are naked and undifferentiated bits 

 of this living matter. But even in their unspecialised protoplasm 

 we find the rudiments of all the properties to be found in the 

 highest animals and the most delicate organs. In the first place, 

 it has the power of assimilation ; it can build up dead matter into 

 its living molecules and transform foreign material into substance 

 like its own. 



Then it is sensitive to stimuli mechanical shock will cause 

 it to contract, strong light or heat will damage it, certain chemi- 

 cals will attract or repel it, electric currents will force it to move 

 in a particular direction. It is out of these primitive properties 

 that all our complex sense-organs have been built up. Because 

 light will alter the protoplasm of an Amoeba, it has been possible 

 for life to evolve an eye. And, be it remembered, the reverse is 

 true. Hertzian or wireless waves are so large that they do not 

 affect simple protoplasm; and no sense-organ has been evolved 

 for their perception. 



The Amoeba uses up oxygen and gives out carbonic acid gas ; 

 it can move ; it grows ; it reproduces. Such are the fundamental 



