194 PHYSIOLOGY 



will move towards the point of the capillary. The movement of the 

 meniscus to or away from the point may thus be used, as in the capil- 

 lary electrometer, to show the direction and amount of any moderate 

 electrical change occurring in a tissue, two points of which are con- 

 nected with the mercury and the acid respectively. It is possible 

 that this electrical alteration of surface tension may be a determining 

 factor in many of the phenomena of movement observed in the animal 

 body. We shall have occasion to discuss this question more fully 

 when endeavouring to account for the ultimate nature of muscular 

 contraction. 



