A cognate operation upon _females_ obtains among the modern Egyptians, the Nubians, the Abyssinians, as well as in many other parts of Africa among the negro races; also among the Malays on the shores of the Persian Gulf (Carsten Niebuhr), and on the banks of the Orinoco. As an ancient custom in Arabia and Egypt, it is noticed by Strabo. Local variations of detail are found; as in the case of the Friendly Islanders just cited; and of the Madagascarians, who cut the flesh at three several times; the excised prepuce being eventually _swallowed_ by some relative or other. The date at which circumcision is performed varies considerably. Among the Jews, the eighth day is, of course, the selected period; probably from consideration for the sacred number seven, for the seven days of uncleanness prescribed for the parturient mother (Lev. xii. 2), and for an idea that with the second cycle of seven days the infant then properly commenced its earthly life. Among the Arabs, it is deferred till the thirteenth year; the age at which their reputed ancestor, Ishmael, was submitted to it. And every race seems to have selected for itself what was considered the most suitable time. The Turks, for example, have chosen the seventh or eighth year; the Persians circumcise boys at thirteen, girls, between the ninth and the fifteenth year; and so on. It is thus evident, not only that the rite is extremely ancient, but that it is impossible to refer the practice of circumcision to any single source; or to doubt that it originally arose among many widely-sundered peoples, as the result of a certain stage in man's mental evolution. The once widely-spread custom of the COUVADE, and other strange aboriginal practices, afford an illustrative analogy.[4] Herodotus seems to have been the author, or at least the introducer, of the cleanliness theory; according to which the ceremony was invented from motives of hygiene. Philo Judæus ascribes the custom to four causes: 1. Cleanliness; 2. The avoidance of carbuncle (Qu. cancer?); 3. The symbolisation of purity of heart; 4. The attainment of numerous offspring.