The distinction which God made between the offerings of Cain and Abel, and His express approval of Abel's offering, might serve to make known, at the time and in succeeding generations, the purport of the promise made originally to Adam, and the ordained conditions of its fulfilment. In fact, the special acceptance by God of Abel's offering may be looked upon as the primary institution of _sacrifice_. The researches of men of learning have abundantly shown that the sacrificing of animals was a very ancient and wide-spread religious practice, but have left altogether unexplained how it _originated_, and whence arose the custom of ratifying a covenant between man and man by _killing_ animals; for what reason also the slaying of _innocuous_ and _helpless_ victims came to be the principal act of religious worship among the Jews, and why it was thought among the Gentiles that such sacrifices _pleased_ the gods. These questions do not appear to admit of answers apart from information derived from Scripture. The answers will, I think, be found to be given by what, in reliance on such aid, has been already said, and by what remains to be said, {24} respecting the covenant of immortality. It is quite possible that, as has happened with respect to other practices, that of sacrificing animals was continued long after its original signification ceased to be understood. This may be affirmed of the ratifying of covenants by killing victims (which no sane person nowadays would think of doing), and generally of the sacrifices offered by Gentile nations in honour of their gods, which eventually became mere matters of _custom_, without any distinct appreciation of their intrinsic meaning. In such cases all clue from tradition or history fails, and the explanation of the sources of the practices can be looked for only in the records of Scripture.