Constellations of morphological, physiological, and psychological traits as earlier proposed by various scholars, such as the Greek physician and philosopher Galen (129–210 A.D.): sanguine, melancholic, choleric, and phlegmatic types; German PSYCHIATRIST Ernst Kretschmer (1888–1961): pyknic (stocky), asthenic (slender), athletic, and dysplastic (disproportional) types; and American PSYCHOLOGIST William Sheldon (1898–1977): ectomorphic (thin), mesomorphic (muscular), and endomorphic (fat) types, based on the relative preponderance of outer, middle, or inner layers of embryonic cellular tissue.