68 THE USE AND NATURE 



The movements of locomotion, or of limited parts of 

 the body, which become established in correspondence with 

 various kinds of external impressions, tend with time to in- 

 crease in number, definiteness, and complexity. They are, 

 for the most part, to be classified as actions subservient to 

 the pursuit and capture of prey, to the avoidance of enemies, 

 to the union of the sexes, or to the care of young. 



All such movements are found, as a general rule, to 

 have the effect of prolonging the action of any influences 

 which previous individual or race experiences have proved 

 to be favourable to the life and well-being of the organism ; 

 and, on the other hand, of cutting short or avoiding influ- 

 ences which past individual or race experiences have 

 proved to be contrary to its general well-being. The 

 capture and swallowing of food are ends to which a very 

 large proportion indeed of the definite motions of most of 

 the lower organisms are directed ; and this direction of 

 their energies is only a special case to be included under 

 the rule above indicated just as efforts to escape from 

 predatory neighbours, are other opposite instances of the 

 same rule. 



Visceral Sensations and the 'Muscular Sense/ 

 In addition to the various modes of impressibility by 

 external influence which we have hitherto been considering, 

 there are also certain other modes due to changes in the 

 condition of internal parts of the organism. These are 

 divisible into two categories : (1) impressions emanating 

 from one or other of the various sets of viscera such 

 as the alimentary canal and its appendages, the respiratory 

 organs, the genital organs, or other internal parts ; and 

 (2) impressions derivable from, or in some way attendant 

 upon, the contractions of muscles. 



The first category of internal impressions those einan- 



