In conclusion, we may supplement these sketches of external culture by mention of a feature that is particularly characteristic of the relation of primitive man to his environment. Primitive man lives in close association with his fellow-tribesmen, but he secludes himself from other tribes of the neighbourhood. He is led to do so because they threaten his means of subsistence; indeed, he himself may fall a prey to them, as do the Pygmies of Central Africa to the anthropophagic customs of the Monbuttus. And yet, primitive man early feels the need of such useful articles as he cannot himself produce but with which he has, in some accidental manner, become acquainted. This gives rise to what is generally called 'secret barter.' An illuminating example of this occurs in the records of the Sarasin cousins as relating to the Veddahs. The Veddah goes by night to the house of a neighbouring Singhalese smith and there deposits what he has to offer in barter, such as captured game, ivory, etc. With this he places a representation of an arrow-head, made of palm-leaves. The next night he returns and finds real arrows of iron which the smith has laid out in exchange for the proffered goods. It might be thought that such a system of barter would imply an excessive measure of confidence. The smith, however, knows that, should he take away that which was brought to him without delivering the arrows, he would himself be struck by an arrow shot from some sheltered ambush. Thus, many things, especially iron, materials for clothing, and articles of adornment, come into the possession of primitive man through secret barter, raising his external culture to a somewhat higher level.