RELATION TO PSYCHIC BEHAVIOR 331 



react positively. In our chapter on reaction under two or more stimuli 

 in the infusoria, many examples of this character are given. 



Indeed, attention in this objective sense seems a logical necessity for 

 the behavior of any organism having at its command more than a single 

 action. The characteristic responses to two present stimuli may be in- 

 compatible with each other. The organism must then react to one or 

 the other, since it cannot react to both; it thus attends (objectively) to 

 one, and not to the other. Only in case there is no reaction at all in 

 the presence of two stimuli, or in case its reaction is precisely inter- 

 mediate between those required by the two, could the basis of attention 

 be considered lacking. An organism behaving in this way would be 

 quickly destroyed as a result of its indecisive and ineffective behavior. 



In higher animals and man we distinguish certain different condi- 

 tions, "states of feeling," "emotions," "appetites," "desires," and 

 the like. In all cases except the self, these various states are distin- 

 guished through the fact that the organism behaves differently in the 

 different conditions, even though the external stimuli may be the same. 

 We find a parallel condition of affairs in the lower organisms. Here, 

 as we have seen, the behavior under given external conditions depends 

 largely on the physiological condition of the individual. Many illus- 

 trations of this fact are given in preceding chapters, so that we need not 

 dwell upon it here. 



In the lower organisms we can even distinguish a number of states 

 that are parallel, so far as observation can show, with those distin- 

 guished and named in higher animals and man. To begin with some 

 of the simpler ones, the objective correlate of hunger can be distin- 

 guished at least as low in the scale as Hydra and the sea anemone. 

 These animals, as we have seen, take food only when hungry, and if 

 very hungry, will take substances as food which they otherwise reject. 

 Doubtless hunger could be detected in still lower organisms by proper 

 experiments. A resting condition comparable to sleep is found, as we 

 have seen, in the flatworm (p. 253), while there seems to be no indica- 

 tion of such a state in the infusoria (p. 181). Fatigue can of course be 

 distinguished in all living things, including separated muscles. 



Correlative with hunger, there exists a state which corresponds so 

 far as objective evidence goes with what we should call in higher animals 

 a desire for food. Hydra when hungry opens its mouth widely when 

 immersed in a nutritive liquid. In the flatworm, we can distinguish 

 a certain physiological condition in which the animal moves about in 

 an eager, searching way, as if hunting for food. Even in Amoeba we 

 find a pertinacity in the pursuit of food (p. 14 and Fig. 21) such as we 

 wouLl attribute in a higher animal to a desire for it. 



