THE CELL AND PROTOPLASM. 55 



duction, or the power of producing new individu- 

 als. From these four simple vital activities all 

 other vital actions follow ; and if we can find an 

 explanation of these, we have explained the living 

 machine. If we grant that certain parts of the 

 body can assimilate food and multiply, having the 

 power of contraction when irritated, we can readily 

 explain the other functions of the living machine 

 by the application of these properties to the com- 

 plicated machinery of the body. But these prop- 

 erties are fundamental, and unless we can grasp 

 them we have failed to reach the centre of the 

 problem. 



As we pass from the more to the less compli- 

 cated animals we find a gradual simplification of 

 the machinery until the machinery apparently dis- 

 appears. With this simplification of the machin- 

 ery we find the animals provided with less varied 

 powers and with less delicate adaptations to con- 

 ditions. But withal we find the fundamental powers 

 of the living organisms the same. For the perform- 

 ance of these fundamental activities there is ap- 

 parently needed no machinery. The simple types 

 of living bodies are simple in number of parts, but 

 they possess essentially the same powers of assimi- 

 lation and growth that characterize the higher 

 forms. It is evident that in our attempt to trace 

 the vital properties to their source we may proceed 

 in two ways. We may either direct our attention 

 to the simplest organisms where all secondary ma- 

 chinery is wanting, or to the smallest parts into 

 which the tissues of higher organisms can be re- 

 solved and yet retain their life properties. In 

 either way we may hope to find living phenomena 

 in its simplest form independent of secondary ma- 

 chinery. 



