The suggestion that owing to peculiarities of diet or of constitution some pestilence afflicted the Egyptians which passed over and spared the Jews, is a very plausible one, and deserves more attention than it has yet received, since it would account for many features in the institution. But there remains another signification, which seems indicated in the thirteenth chapter of Exodus in connection with the institution of the Passover. There we read the order, "Thou shalt set apart [the margin more properly reads "cause to pass over"] unto the Lord, all that openeth the matrix" (verse 12). "And every firstling of an ass thou shalt redeem with a lamb; and if thou will not redeem it, then thou shalt break his neck: and all the firstborn of man among thy children shalt thou redeem."* Professor Huxley asks upon this passage: "Is it possible to avoid the conclusion that immolation of their firstborn sons would have been incumbent on the worshippers of Jahveh, had they not been thus specially excused?"** In one of the oldest portions of the Pentateuch (Exodus xxii. 29) the command stands simply, "the firstborn of thy sons shalt thou give unto me." In Exodus xii. 27, xxiii. 18, xxxiv. 25; and Numbers ix. 13, the Passover is spoken of as particularly the Lord's own sacrifice. * Why is the ass only mentioned besides man? One cannot but suspect that his introduction is an interpolation by the reformed Jews, who had outgrown the custom of human sacrifice, betrayed by the phrase "thou shalt break his neck." ** Nineteenth Century, April, 1886. The law proceeds to enjoin that the father shall tell his son as the reason for the festival, how the Lord "slew all the firstborn in the land of Egypt, both the firstborn of man and the firstborn of beasts: therefore I sacrifice to the Lord all that openeth the matrix being males; but all the firstborn of my children I redeem." Evidently here is the notion of a substitutionary offering, although the reason given is not the true reason. In Exodus xxxiv. 18-20, the festival is brought into the same connection with immediate reference to the redemption of the firstborn. In the story of Abraham and Isaac we have the same idea. God commands the patriarch to offer up his only son as a burnt sacrifice (Gen. xxii. 2), an order which he receives without astonishment, and proceeds to execute as if it were the most ordinary business imaginable, without the slightest sign of reluctance. A messenger from Jahveh, however, intervenes and a ram is substituted.* I do not doubt that this story, like similar ones found in Hindu and Greek mythology, indicates an era when animal sacrifices were substituted for human ones.** * Observe that Elohim, the old gods, claim the sacrifice and Jahveh, the new Lord, prevents it.