General paralysis is often very difficult to diagnose, and the responsibility of coming to a decision is not lessened by the fatal character of the disease. Amongst the protean manifestations of neuro-syphilis, the early and definite recognition of this, its most deadly and intractable form, offers a problem in nice discrimination—a problem which is in the present tense and imperative mood. According to Southard, of 119 cases diagnosed as general paralysis, post-mortem examination revealed a diagnostic error of 26 per cent. If anyone had been able to devise a less intricate test for syphilis, the Wassermann reaction would never have survived to the present day. It is one of the most complicated methods that have been applied to diagnosis in medicine. Any simple test, therefore, which promises increased precision in diagnosis, is worthy of that careful investigation which is the half-way house to knowledge.