46 PHYSICAL EXPRESSION. 



(kinetic action). The mechanism for a reflex 

 movement requires (a) sensory surface ; (6) an 

 afferent nerve-fibre ; (c) a nerve-centre ; (d) an 

 efferent or motor nerve ; (e) a muscle ; such ap- 

 paratus may be congenital or acquired. Probably 

 reflex action has a large share in that faculty of the 

 brain which produces mind, and which is here called 

 " mentation." 



" Reflected action " is a term used to indicate a 

 passive condition of the subject, expression resulting 

 from the mode in which it reflects an afferent force, 

 such as light ; such is the mode of expression in 

 a statue. Expressions by form and colour are 

 similar modes. 



Sound produced by a living being is a result of 

 movement, and as such is highly expressive. 



Change of function is an important mode of 

 expression; it may be studied in vegetable cells, 

 glands, etc. 



Movements (kinesis) and the results of movement 

 are among the most important modes of expression, 

 and these are conveniently termed " kinetic," in 

 contrast to " trophic modes " which affect the material 

 structure of the subject. 



Coincident development, proportional and similar 

 development in the members or parts of a living- 

 subject, are interesting modes of expression ; they 

 are trophic in kind. These are discussed in 

 chap. xvi. 



The facts of heredity are very important and 

 complex modes of expression ; some facts concerning 



