Samuel Leeson Leonard, Cornell professor emeritus of zoology, died Nov. 12 in Ithaca, N.Y., at age 101. He is known for discovering in the late-1920s that estrogen could be used as a contraceptive -- the finding that led to the creation of the birth control pill, which contributed to women's liberated attitudes toward sex and the sexual revolution of 1960s.

In 1931 Leonard also authored a seminal paper that reported that the ovaries and testes were regulated by two pituitary gonadotropic hormones: the follicle-stimulating hormone and the luteinizing hormone.

Leonard was born Nov. 16, 1905, in Elizabeth, N.J., and grew up in Arlington, N.J. As a child he played the saxophone in a band that celebrated Liberty Ship launches and saluted soldiers leaving for the European battlefields of World War I. He earned his bachelor's degree from Rutgers University (1927) and both his master's (1929) and doctoral (1931) degrees from the University of Wisconsin.

After working as a National Research Council Fellow at Columbia University and an assistant professor at Union College and Rutgers University, Leonard joined the Cornell faculty in 1941. He became a full professor in 1949.

By his retirement in 1971, he had taught Cornell's freshman zoology course to about 9,000 students.

Leonard's wife, Olivia L. Rees-Leonard, and his son, David L. Leonard, predeceased him. He is survived by a daughter, Patricia Hoard of Warwick, N.Y., four grandchildren and three great-grandchildren.