The demonstration by Noguchi and many other investigators after him of spirochætes in the nervous texture in tabes dorsalis and in dementia paralytica has, as is well known, quite subverted the old conception of these diseases as para- or metasyphilitic in nature. They are just as syphilitic as other diseases caused by Spirochóta pallida are. It is quite a different thing, however, that in certain respects they occupy a peculiar position; as a rule they do not manifest themselves till ten to fifteen years after the primary affection, and they are very little affected by antisyphilitic treatment. It is well known that it was especially this last fact which caused them to be considered as not syphilitic in the common sense.