Celsus goes on to say: “Let any one inquire of the Egyptians, and he will find that everything, even to the most insignificant, is committed to the care of a certain demon. The body of man is divided into thirty-six parts, and as many demons of the air are appointed to the care of it, each having charge of a different part, although others make the number much larger. All these demons have in the language of that country distinct names; as Chnoumen, Chnachoumen, Cnat, Sicat, Biou, Erou, Erebiou, Ramanor, Reianoor, and other such Egyptian names.
Moreover, they call upon them, and are cured of diseases of particular parts of the body. What, then, is there to prevent a man from giving honour to these or to others, if he would rather be in health than be sick, rather have prosperity than adversity, and be freed as much as possible from all plagues and troubles?” In this way, Celsus seeks to degrade our souls to the worship of demons, under the assumption that they have possession of our bodies, and that each one has power over a separate member.
And he wishes us on this ground to put confidence in these demons of which he speaks, and to serve them, in order that we may be in health rather than be sick, have prosperity rather than adversity, and may as far as possible escape all plagues and troubles. The honour of the Most High God, which cannot be divided or shared with another, is so lightly esteemed by him, that he cannot believe in the ability of God, if called upon and highly honoured, to give to those who serve Him a power by which they may be defended from the assaults directed by demons against the righteous. For he has never beheld the efficacy of those words, “in the name of Jesus,” when uttered by the truly faithful, to deliver not a few from demons and demoniacal possessions and other plagues.
Source: Against Celsus (New Advent)