Dr. Stradonitz, in a long paper, recommends historical research in connection with hereditary disease, and prescribes some methods of inquiry which are sufficiently obvious. Every one has two parents and four grandparents, and in this ratio his ancestors might go on doubling at each generation, till three hundred years back the ascendant roll might have 1024 persons. Actually this never takes place through the marriage of cousins in the first, second, and farther degrees.