IO4 WALLACE CRAIG. 



The time occupied by a cycle varies extremely, from cycles 

 measured in seconds to those that occupy a year or even longer. 

 The relative duration of the phases also is extremely variable. 

 In some cases the appeted situation is attained without delay, 

 and Phase I. thus passes so rapidly as to be overlooked by the 

 observer. In other cases the bird strives hard to overcome great 

 obstacles which stand in the way of the attainment of the appeted 

 stimulus, consequently Phase I. is of long duration. Phase II. 

 may last, in the case of drinking, about one second; in the case 

 of incubation, about three weeks. 



It should be stated, too, that the phases are not sharply separ- 

 ated; each passes more or less gradually into the next. Thus, 

 from Phase IV. of one cycle in a series to Phase I. of the suc- 

 ceeding cycle, there is often a gradual rise of appetite; active 

 search for satisfaction does not commence until a certain inten- 

 sity of appetite is attained. This is what is known in pedagogical 

 literature as "warming up." This gradual rise of the energy 

 of appetite is followed (Phase II. III., or 1 1. -IV.) by its sudden 

 or gradual discharge. This rise and discharge are named by 

 Ellis ('03), in the case of the sex instinct, "tumescence" and 

 "detumescence." They are important phases in the psychology 

 of art, in which sphere they are named by Hirn ('oo) "enhance- 

 ment" and "relief." The discharge (Phase II.) is also exempli- 

 fied in "catharsis" in art and in psychiatry. 



The cycles in the behavior of birds are fundamentally the same 

 phenomenon as the cycles in human behavior. Human cycles 

 are enriched by an intelligence far surpassing that of doves, but 

 this is a difference of degree only. If the dove's cycles are deter- 

 mined largely by instinct, habit, physiological conditions, and 

 not intelligence, so are some human cycles, as those of sleeping, 

 eating, drinking, sex. F. H. Herrick ('10, 83) emphasizes the 

 fact that a bird may scamp one cycle in order to begin another. 

 Thus, birds may abandon young w r hich are not yet weaned, be- 

 cause their appetence for a new brood has set in. But the same 

 principle works, though not quite so crudely, in human life; as in 

 the case of a mother who grows indifferent or even somewhat 

 hostile toward her older children each time a new child is born. 

 Herrick emphasizes also the fact that when anything disturbs 



