A separate enumeration of mulattoes has been made four times—in 1850, 1860, 1870, and 1890 respectively. The census authorities themselves said that the figures were of little value, and any attempt to distinguish Negroes from mulattoes was abandoned in the census of 1900. If a person is apparently white, the census enumerator will feel a delicacy in asking him if he has Negro blood in his veins. If the enumerator does ask the question and if the other is honest in his answer, it is often that the latter does not know his own ancestry. Dr. Booker T. Washington, for instance, has said that he does not know who his father was.[10] Marital relations among Negroes during slavery were so irregular, and illicit intercourse between white men and slave women was so common that the line of ancestry of many mulattoes is hopelessly lost. But Mr. Baker makes the rough estimate, which doubtless is substantially correct, that 3,000,000 of the 10,000,000 (_circa_) Negroes are visibly mulattoes. This one third of the total Negro population represents every degree of blood, of color, and of physical demarcation from the fair complexion, light hair, blue eyes, thin lips, and sharp nose of the octoroon, who betrays scarcely a trace of his Negro blood, to the coal-black skin, kinky hair, brown eyes, thick lips, and flat nose of the man who has scarcely a trace of Caucasian blood. It is this gradual sloping off from one race into another which has made it necessary for the law to set artificial lines. The difficulty arising from the intermixture of the races was realized while the Negro was still a slave. Throughout the statutes prior to 1860, one finds references to “persons of color,” a generic phrase including all who were not wholly Caucasian or Indian. This antebellum nomenclature has been brought over into modern statutes. It is surprising to find how seldom the word “Negro” is used in the statutes and judicial decisions. Some States have fixed arbitrary definitions of “persons of color,” “Negroes,” and “mulattoes”; others, having enacted race distinctions, have then defined whom they intended to include in each race. This has been done particularly in the laws prohibiting intermarriage. The Constitution of Oklahoma[11] provides that “wherever in this Constitution and laws of this State, the word or words, ‘colored,’ or ‘colored race,’ or ‘Negro,’ or ‘Negro race,’ are used, the same shall be construed to mean, or apply to all persons of African descent. The term ‘white’ shall include all other persons.”