Published online by Cambridge University Press: 15 May 2009
1. In the foregoing experiments evidence is adduced to show that bacteria in spleen broth or neutral Ringer's solution carry a negative charge and move to the anode in an electric field. The addition of a slight trace of a positive trivalent ion such as La or Ce or Yb to the solutions containing the bacteria immediately lessens or neutralises this negative charge, and if the concerntration of these ions is further increased completely abolishes it, and the bacteria undergo flocculation or agglutination. Living bacteria seem much more sensitive to the action of these ions than non-living colloidal particles. The addition of negative trivalent ions to bacterial cultures is without any effect on their movement in an electric field; the negative charge on the bacteria is not increased.
2. Some inconclusive evidence has been brought forward in support of Girard and Audubert's work regarding the influence of the double electric layer of the bacterial cell wall in controlling their biological properties.