The self-knowledge that doctors give--Insidious approach of many diseases--Medical views of the old of body and mind (senile dementia)--Charcot--G. M. Humphrey--Sir James Crichton-Browne--H. M. Friedman--H. Gilford--H. Oertel--A. S. Warthin--W. Spielmeyer--I. L. Nascher-- Sir Dyce Duckworth--Robert Saundy--Arnold Lorand--T. D. Crothers--C. G. Stockton--W. G. Thompson--M. L. Price-- G. S. Keith--J. M. Taylor--C. W. Saleeby--C. A. Ewald-- Raymond Pearl--Protest against the prepotence of heredity in determining longevity. VI. THE CONTRIBUTIONS OF BIOLOGY AND PHYSIOLOGY 248 Weismann’s immortality of the germ plasm and his denial of the inheritance of acquired qualities--The truth and limitations of his views--The theories of Hering and Simon--Metchnikoff’s conception of the disharmonies in man, of the rôle of intestinal fauna and their products, of euthanasia, and of the means and effects of prolonging life--C. S. Minot’s conception of the progressive arrest of life from birth on as measured by declining rate of growth, and his neglect to consider the dynamic elements-- C. M. Child’s studies of rejuvenation in lower and higher forms of life in the light of the problems of senescence-- J. Loeb’s studies of the effects of lower temperature, of toxins and ferments--The preservation of cells of somatic tissues potentially immortal under artificial conditions-- Account of the studies of Carrel, Pozzi, and others-- Investigations upon the effects on sex qualities and age of the extracts and transplantations of glands, from Claude Bernard--Investigations of Eugene Steinach on the interchange of sex qualities and rejuvenation by glandular operations in animals and man--G. F. Lydston’s work-- Serge Voronoff’s experiments and his exposition of the achievements and hopes of glandular therapy--Some general considerations in view of work in this field. VII. REPORT ON QUESTIONNAIRE RETURNS 319