Multiple sclerosis is often referred to as a rare and mysterious disease. It is probably neither. In the five years from 1931 to 1935 the diagnosis of multiple sclerosis was made for 204 new patients admitted to the Boston City Hospital (approximately 1,800 beds). The corresponding figure for poliomyelitis during the same years was 100, for encephalitis 101 and for proved subacute bacterial endocarditis fifty. In evaluating these statistics it should be noted that no particular effort was being made to bring patients with multiple sclerosis into the hospital for study, as the investigation of multiple sclerosis was being carried out on purely experimental lines and no form of special treatment was being offered. The Boston City Hospital is one of the few hospitals in Boston to which patients with poliomyelitis in the early stage are admitted. While the statistical value of the figure given is open to question, it