LECTURE IV. 

 ORGANISM AND MECHANISM. 



§ 1. Is Organism More than Mechanism? §2. Chemical and 

 Physical Laws apply to Organisms. § 3. Some Difficulties in 

 the Application of Physical and Chemical Formulce to Organ- 

 isms. § 4. Criticism of Mechanistic Descriptions of Everyday 

 Functions. § 5. Criticism of Mechanistic Descriptions of 

 Animal Behaviour. § 6. Difficulty of Applying Mechanistic 

 Formulce to Development. § 7. Difficulty of Applying Mecha- 

 nistic Formula; to Organic Evolution. § 8. Answers to Criti- 

 cisms. 



§ 1. Is Organism More than Mechanism? 



According to Kirchhoff's famous definition (1876), the 

 task of mechanics is ^' to describe completely and in the sim- 

 plest manner the motions which take place in nature ". 

 When we give a mechanical description of an occurrence 

 — the eruption of Vesuvius, the bursting of the broom-pods, 

 or the curling of the non-living tendrils of a mermaid's purse 

 — it is in terms of matter and motion, or in chemico-phvsical 

 terms which are believed to be reducible to those of matter 

 and motion. The mechanical account is as such entirely 

 satisfactory when it enables us to see a process as a con- 

 tinuous series of necessarily concatenated mechanical opera- 

 tions like those which occur in the slow movement of a 

 glacier, or like the successive explosions which mark the 

 extension of a rapidly spreading conflagration. We shall 

 use the slightly wider term mechanistic to include cither a 

 matter-and-motion description, which is in the strict sense 

 mechanical, or a more dynamical description in which the 



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