GROWTH AND MOVEMENT COMPARED. 281 



We will compare descriptions of growth and 

 descriptions of movement. It is very desirable to 

 know how to give scientific descriptions. A 

 description may be given of the body of a 

 tadpole and the body of a frog ; the difference 

 between the two is the growth or development of 

 the individual. The description would be much 

 more perfect if all the stages of the growth 

 were given ; the greater the number of " stages 

 of growth" given, the fuller and more com- 

 plete the description. Now contrast this with the 

 description of the movements of the hand. We 

 may observe the open " straight extended hand," 

 followed immediately by the " convulsive hand ; " we 

 thus note two passive conditions, or postures, states 

 of quiescence : the difference between them is an 

 indication of the movement that has occurred. The 

 description might be given by stating all the move- 

 ments that actually occurred, flexion of all the 

 joints of all the digits with adduction of the thumb 

 upon the palm. 



Again, in each of the examples the description 

 might be given with great exactness and fullness, 

 by recording the combinations and sequences of 

 trophic and kinetic action as they occur, in time, 

 quantity, and kind. 



The object specially in view, in thus insisting 

 on such methods of description, is the attempt 

 to bring biological processes within the range of 

 calculation. And it is also desirable to have a 

 common form of expression of trophic and kinetic 

 energy, so that we may more easily apply the same 



