THE PHENOMENON OF CONTRACTION. 59 



may conduct a stimulus or impulse to other cells even after its 

 own cilia have lost their contractility. This fact is particularly 

 significant in general physiology, as it aids in showing that the 

 property of conductivity which is exhibited in such high degree 

 by nerve fibers is possessed to a lower degree by other tissues. 

 The ciliary movement is affected by variations in temperature, and 

 if the temperature passes beyond an optimum point the cilia fall 

 into a condition resembling heat rigor in the muscle. Their move- 

 ments are affected also by the reaction of the medium, being at 

 first accelerated and then slowed or destroyed by a slight degree 

 of acidity and favored by a very slight degree of alkalinity.* 



* References for physiology of ciliary movement: Verworn, "General 

 Physiology," English translation by Lee; Piitter, " Ergebnisse der Physiol- 

 ogie," 1902, vol. ii, part ii; Engelmann, article, "Gils vibratils," io Richet's 

 ■" Dictionnaire de Physiologie," vol. iii, 1898. 



