66 DISEASE IN PLANTS. 



US only on the threshold of the real problem. He 

 has stood outside the factory in which the real 

 work we want to know about is being carried on, 

 and has told us of so many tons of this material 

 being carried in at the gates, and of so many tons 

 of that coming out ; he has even burnt down the 

 factory, and all its contents and machinery, and 

 has then told us how many tons of the various 

 materials were there at the time ; but this is not 

 what we want, valuable as the information is, and 

 still more will be. What we want, and what we 

 expect to obtain, is more information regarding 

 what is done with the materials in the factory: 

 what machinery they are put into, and how they 

 are put in : what stages they go through, and how 

 the stages follow one another : what wear and 

 tear has to be endured, and how we can step in 

 and stop the working of the machine for our own 

 benefit at the best possible time. 



The physiologist proceeds empirically, by experi- 

 menting with the living machinery. He recognises 

 the parts and their structure, and tries to find out 

 what they are doing : he knows that the laws of 

 physics and chemistry cannot be traversed, but he 

 sees these laws at work under special and very 

 complex and peculiar conditions. He therefore, 

 as the results of his experiments, sets new questions 

 or old questions under new conditions, if you 

 like and undoubtedly wants the help of both 

 chemist and physicist ; or, if it is preferred, the 

 chemist and physicist may attack the problems, 

 but they must familiarise themselves with the 



