Development of specific methods for elastin: Investigations of relations between dye configurations and selectivity for elastin will be continued to identify dyes which stain elastin selectively. Development of selective stains for pseudo-elastica: Selective coloration of pseudo-elastica by "elastica stains" is unsatisfactory because of the widely held belief that these stains are specific for elastic tissue. Various dyes and metal-dye complexes will be tested as substitutes. Selective methods for basement membrane collagen: Currently available methods visualize the carbohydrate fraction of basement membranes. Therefore, development of selective methods for the collagen moiety appears desirable. Studies of arterial lesions in children and adults will be continued. New technics developed during the year will be applied where indicated. Observations will be correlated with data on age, sex, race and clinical history, especially family history of cardiovascular diseases. Histochemical differences between myosins, especially between myosin in A bands of striated muscle and in vascular muscle cells will be investigated. Histochemistry of pulmonary collagen: Collagen in pulmonary arteries and in the parenchyma will be investigated.