A number of investigators have studied the nature of the electric charge of bacteria. Bechhold (1904) was the first to record the fact that bacterial cells carry a negative charge. Cernovodeanu and Henri (1906) studied a larger series of bacteria and reported that all species, except B. dysenteriae (Flexner), carried a negative charge; but the claim that the dysentery bacillus is electropositive has been contradicted by Szent-Gyorgi (1921). Since then a number of investigators have reported that bacteria migrate to the anode (Szent-Gyorgi (1921); Putter (1921); Winslow, Falk, and Caulfield (1923); Govaerts (1923)). Winslow and his co-workers (1923, 1924) used the microscopic cell devised by Northrop (1922) to study the electrophoretic migration of a large number of microörganisms under a wide range of pH values. This method enabled the authors to determine the migration velocities of various microörganisms and particles in substrates having various pH values.