VITALITY 



467 



stimuli were operating and that a perfect equilibrium was established 

 throughout. 



Vitality, as the sum total of all the protoplasmic activities set 

 up in response to internal and external stimuli is variable. Varia- 

 tions due to external conditions may be readily seen in the effects 

 of heat and cold. Increased temperature increases oxidation leading 



C 



^Saifr-" 



Fig. '195. — Uroleptus mohilis. Division of double individual; type with two divis- 

 ion nuclei. A, stages in the fusion of the two set.s of macronuclei independently; 

 B, two division nuclei and two new peristomes; C, division of the cell each half with 

 two sets of nuclei. (After Calkins.) 



to more rapid movements including food-taking activities, more 

 active digestion, assimilation, growth and reproduction. It in- 

 volves more waste and more active pulsation of the contractile 

 vacuole. Conversely decreased temperature slows u}) the entire 

 series of activities and vitality is reduced. In like manner any 

 condition of the environment which tends to quicken, to weaken, 



