Lysosomes, discovered by Christian de Duve in 1952, and since shown to be characteristic constituent organelles of all cells, are very important containers of acid hydrolases and perhaps other digestive enzymes. The functions of these enzymes relate to extracellular digestion of cells, intracellular digestion, and self-lysis of the cell. The lysosomal enzymes affect carbohydrate and lipid metabolism, and genetic deficiencies in enzymes produce such diseases as glycogen storage disease, and Tay-Sachs and other neurological diseases. Tay-Sachs disease is discussed as an example. It is produced by a deficiency of hexosaminidase A. It is a recessive autosomal condition in its inheritance. Both the heterozygotes and the affected fetus may be detected by tests for hexosaminidase A. Amniocentesis may be used to diagnose the homozygous condition, which is fatal by the third year of life, and an abortion may then be performed. A variety of psychological, ethical, and legal questions, as well as biological and medi...