The "Wassermann" blood test for syphilis is now generally recognized as a valuable aid to the clinician, not only in the diagnosis of the disease, but often as an indicator of the effect of treatment. It is not, perhaps, so generally appreciated, however, that the test, in order to be of real value, must be so carried out that a "positive" reaction will be obtained only in syphilis and in certain other conditions that are readily distinguished from syphilis. No one, thus far, has succeeded in so improving the efficiency of the test that in every case of syphilis with apparent lesions a positive reaction is obtained; so that as a diagnostic means a negative "Wassermann" reaction offers no guarantee of the absence of luetic infection; but properly performed, the test, when it resultspositively, must be expected to indicate either syphilis or certain other easily recognized conditions,