4. What is the classical differential diagnosis between paretic neurosyphilis and neurasthenia? The testing of the blood by the W. R. is unconditionally necessary. If the W. R. is negative, the diagnosis of paretic neurosyphilis is extremely improbable. (It must be borne in mind that a number of cases of paretic neurosyphilis have been shown to have a negative W. R. in the serum, and receive a proper diagnosis only after spinal fluid examination.) Next to the serum W. R. stand the pupillary and aphasic symptoms. In the presence of Argyll-Robertson pupil or even a slight speech defect, the diagnosis of neurasthenia must certainly be made with caution if at all. Kraepelin remarks: The sudden occurrence of neurasthenic disorders in a male of middle age without any evident cause therefor is always suspicious. Yet it must be emphasized that a complaint of occasional dizziness, slight speech defect, tremor of tongue, and a moderate increase of tendon reflexes do not possess any marked diagnostic significance. Clear insight and understanding of the nature of the disease phenomena, a persistent search for recovery, reasonableness in conversation, progressive improvement under appropriate treatment, speak for neurasthenia. Joffroy and Mignot differentiate what they call preparetic neurasthenia from other neurasthenic states, not only on the basis of its etiology but on the basis of its symptoms. They also call attention to the fact that neurasthenia, being a pure neurosis, develops either on a manifestly hereditary basis or upon some physical injury, weakening disease, or moral shock. The pure neurotic suffers a great deal more than the patient who is destined to become a victim of paresis. The character change in neurasthenia does not amount to that entire transformation of personality (even to the performance of criminal acts) that we find in paretic neurosyphilis; at the most, the neurasthenic shows minor emotional disturbances and a certain pathological egoism. The psychotherapeutic test also rather readily dissipates many of the neurotic, hypochondriacal fears and feelings. Although both pure neurasthenia and the paretic pseudoneurasthenia are characterized by sexual weakness, the sexual anæsthesia of the preparetic is practically always preceded by a stage of sexual over-excitement. These finer clinical indications, however, fade into insignificance beside the data that can and should be obtained from laboratory tests.