416 PLANT PHYSIOLOGY 



One can examine the water before it enters the fall and after it 

 leaves but not while in motion, or the fall ceases to exist. In like 

 manner, in the complex equilibria of the organism, the worker 

 seldom or never has the opportunity to pry into the mechanism 

 while in motion. He can examine the elements which go to make 

 up the organism and he can examine them after they have been 

 fixed and stained, but he is no longer examining living material. 

 The quality which made it different is not there. Is the motion 

 itself the life? Is life merely the constant interplay of molecule 

 with molecule and death the absence of such motion? What makes 

 this interplay of parts? When a clock stops it can be started again. 

 Why cannot the organism be started when it stops? 



2. The physical tools problem. The natural scientist can con- 

 cern himself only with the world of material reality. His work 

 lies within the realm of the senses, and the only forces for which 

 his tools are of any value are physical forces, that can be weighed 

 and measured. // there were forces operating in the world of im- 

 material reality, they could not be demonstrated until they were 

 changed into physical forces. One should realize that the senses 

 are limited in their scope; the eye is sensitive to rays of a definite 

 wave length, and it was consequently many years before the 

 shorter waves, which the eye cannot perceive, were detected by 

 other means. If such extraphysical forces exist, they can be man- 

 ifested only through the known physical ones, and the fact that 

 they are not perceived as such does not prove their absence. 



3. The egocentric predicament. The fact that the mind, which 

 reasons, is never in contact with the facts about which it reasons 

 is also much to be deplored. All our knowledge must reach the 

 brain in the skull through the nerve channels. The brain is never 

 in direct contact with the external world. All of its information is 

 secondhand, and there are numerous instances which show how 

 unreliable this information often is. This is a real predicament 

 but one with which we must content ourselves. 



Mechanism a Working Hypothesis. — These problems are called 

 to our attention not to bolster up vitalism or to detract from mech- 

 anism but to present the problem in its true light. The mechanists 

 have done much more than the vitalists in solving our problems. 

 The mechanistic hypothesis has been the most fertile and, in 

 fact, is the only one which has advanced our knowledge of the 

 physical world about us. But mechanism is a method and should 



