12 THE STORY OF THE LIVING MACHINE. 



reign of law, purpose could not exist in nature. 

 Only cause and effect appeal to him. The present 

 phenomena are the result of forces acting in the 

 past, and the scientist's search should be not for 

 the purpose of an adaptation, but for the action 

 of the forces which produced it. To discover the 

 forces and laws which led to the development of 

 the present forms of animals and plants, to ex- 

 plain the method by which these forces of nature 

 have acted to bring about present results, these 

 became the objects of scientific research. It no 

 longer had any meaning to find that a special 

 organ was adapted to its conditions; but it was 

 necessary to find out how it became adapted. 

 The difference in the attitude of these two points 

 of view is world-wide. The former fixes the at- 

 tention upon the end, the latter upon the means 

 by which the end was attained; the former is 

 what we sometimes call teleological, the latter sci- 

 entific ; the former was the attitude of the study 

 of animals and plants before the middle of this 

 century, the latter the spirit which actuates mod- 

 ern biology. 



The Mechanical Nature of Living Organisms. 

 This new attitude forced many new problems to 

 the front. Foremost among them'and fundamen- 

 tal to them all were the questions as to the me- 

 chanical nature of living organisms. The law of 

 the correlation of force told that the various 

 forms of energy which appear around us light, 

 heat, electricity, etc. are all parts of one common 

 store of energy and convertible into each other. 

 The question whether vital energy is in like man- 

 ner correlated with other forms of energy was 

 now extremely significant. Living forces had been 

 considered as standing apart from the rest of na- 



