=Physically=, there was no neurological disorder. The patient appeared rather under-nourished. The heart borders lay 2 cm. to the right and at 11½ cm. to the left of the mid-sternal line. The aortic second sound was very loud. There was a moderate radial arteriosclerosis. Systolic blood pressure was 210, diastolic 155. The high blood pressure suggested nephritis, possibly of arteriosclerotic origin, but urine examination and blood-nitrogen tests yielded no evidence of kidney disease. Moreover, it is our experience that a manic-depressive psychosis in persons past middle life is not infrequently complicated by high blood pressure. In point of fact, some authors insist upon a relation between manic-depressive psychosis and the arteriosclerosis which rather frequently sets in in this disease. Routine examination of the blood serum, however, yielded a positive W. R. Following the approved rule of making an examination of the spinal fluid in all mental cases having a positive serum W. R., we proceeded to lumbar puncture. The fluid was clear and contained 35 cells per cmm., the albumin was in excess, and there was a positive globulin reaction. The gold sol reaction was of the “paretic” type; the W. R. was strongly positive. On this basis, it seems worth while to consider the diagnosis of GENERAL PARESIS or that of some form of non-paretic neurosyphilis. The former is the diagnosis which we prefer. 1. What is the classical differential diagnosis between manic-depressive psychosis and neurosyphilis? The laboratory tests have naturally supplanted the older purely clinical methods of differential diagnosis. The difficulties lodge, in the first instance, in depressive states. It would appear to be impossible on purely clinical grounds in certain cases to tell the depression of neurosyphilis from the depression of manic-depressive psychosis, since the slightly greater interest in the outer world taken by manic-depressive patients and their greater responsiveness to diagnostic threats (suggestion that patient is to be pinched or cut) are of no special value in the individual case. Identical considerations hold for the maniacal phases of manic-depressive psychosis, for these maniacal phases may even develop delusions (Kraepelin) of precisely the same nature as the characteristic expansive delusions of the excited paretic. 2. If the clinical symptoms are insufficient in differential diagnosis, are not the pupillary signs and the speech defect of greater value? They are of value if present, but as in the case of Agnew, the victim of neurosyphilis may show no pupillary or speech disorder. Instances are familiar, also, in which the pupillary and speech signs are absent in very advanced cases of non-paretic or even of paretic neurosyphilis.