+586+. The objects affected by the conception of taboo are as various as the conditions of human life--they include things inanimate and animate, and events and experiences of all sorts. Sometimes the danger is supposed to be inherent in the object, sometimes the quality of dangerousness is imposed on it or infused into it by some authority; but in all cases there is present the force (mana) that, in savage theory, makes the external world a factor in human destinies.[939] This force may be transmitted from one object to another (usually by contact[940]), and thus the taboo infection may spread indefinitely, a silent and terrible source of misfortune, sometimes to a single person, sometimes to a whole community. Ceremonies connected with taboo are designed to protect against this destructive influence. +587+. The principal taboo usages may be classed roughly under certain heads, which, however, will sometimes overlap one another. +588+. _Taboos connected with the conception of life._ For early man the central mystery of the world was life, and mystery and danger attached to all things connected with its genesis, maintenance, and cessation--to pregnancy, birth, death, corpses, funerals, blood. Against these things precautions, in the form of various restrictions, had to be taken. Pregnancy was sometimes regarded as due to supernatural agency, and in all cases was noted as a mysterious condition in which the woman was peculiarly exposed to evil influences; she was sometimes required to keep her head covered or to avoid moonshine, or to live separated from her husband.[941]