The population of the United States has increased approximately 50% in the last 30 years. During this same period, life expectancy at birth has increased from 60 to 70 years. In terms of the total number of deaths from all causes, it is estimated that the number of those who died from lesions within the nervous system has changed but little in these 30 years, having increased from about 14% to 17%. Striking therapeutic triumphs during this period have been achieved in the reduction in the number of deaths from infections and deficiency diseases involving the nervous system. Thus, deaths from infections primarily involving the nervous system have been reduced by more than half, and deaths from infections secondarily involving the nervous system, such as tuberculosis and syphilis, are an eighth of what they were 30 years ago. However, these gains are small, contrasted with the staggering increase in the