The Spirochæta pallida, concerning the etiologic rôle of which in syphilis there now is no question, has been demonstrated in chancres, syphilids, the tissues in cases of congenital syphilis, gummas, and in a few cases of syphilitic aortitis, but in so-called parasyphilitic disease, e. g., general paralysis, it as yet has not been seen. By means of the Wassermann reaction, however, chemical changes peculiar to syphilis have been demonstrated in the blood serum of individuals suffering from general paralysis and locomotor ataxia and on this account the question arises as to the exact relation between the spirochete and parasyphilitic diseases. For the purpose of illuminating certain phases of this problem Browning and McKenzie1 call attention to the points of resemblance between syphilis and trypanosomiasis. The principal points are: In trypanosomiasis the infecting agent is a protozoon, and this, they say, probably also is the case in syphilis; in experimental