290 



University of California Publications in Zoology [Vol. 11 



VII. INFLUENCE OF INTERNAL STATES 



1. Behavior of Well-Fed Leeches 

 Leeches fed to satiety the evening before and left in the dish 

 overnight with an abundant supply of crushed snail for food 

 were tested for the duration of swimming response as evoked 

 by fifteen successive contact stimulations. The comparative 

 curves (see fig. 12) derived from the data given in the following 

 table (see table XVI) show the sluggishness of the well fed 

 individuals as opposed to the responsiveness of the normal speci- 

 mens. In this condition of satiety the same general dullness of 

 response to .stimuli of all kinds is evidenced, as is characteristic 

 of the duration of swimming. The results given in table XVI 

 represent the duration in seconds of the swimming response 

 evoked by posterior end stimulation of comparatively uniform 

 intensity. The average height of the curve of the normal indi- 

 viduals is to be observed as considerably above that of the well 

 fed individuals. The condition of the organism when fed to 

 satiety suggests from the nature of its effect on the responsive- 

 ness of the animal a close resemblance to what is secured upon 

 partially fatiguing the individual. 



--^^ ^ I I I I I I -{- 2^ ^ ^T" J Bli""^" txXTT ("TTT"""T" 



^'""IimT[TT|^^""""'I"''B'" 



Fig. 12. — Curve showing comparative responsiveness of normal and 

 well-fed individuals to contact stimulation. Dotted line represents re- 

 sponses of normal leeches; solid line, the well fed. 



