This journal provides immediate access to some articles. Volume 31(4); April 1945 Article Awards to the Academy and Research Council PMCID: PMC1078771 Chemistry Vitamin A in Relation to Aging and to Length of life PMCID: PMC1078768 Mathematics Axiomatic Approach to Homology Theory PMCID: PMC1078770 Irregular Projective Invariants PMCID: PMC1078772 Euler's Three Biquadrate Problem PMCID: PMC1078773 Pathology The Law of Mass Action in Epidemiology: II PMCID: PMC1078769 Erratum Dominance Modification and Physiological Effects of Genes PMCID: PMC1078774 Corrects: Dominance Modification and Physiological Effects of Genes. Proc Natl Acad Sci U S A. 1945 February; 31(2): 82–84. Journal Matter Original table of contents page Administrative content — journal masthead, notices, indexes, etc. | ||