FIG. 23. Apparatus for cataphoretic experiments with dyes.^** The wires 



from a 12-volt accumulator are marked — and +. Methylene green (a 



basic dye) is being tested. The current has been passing for 42 hours. For 



full description see accompanying text and Appendix (p. 321). 



(Photograph by Mr P. L. Small) 



