It is, of course, impossible to argue that the fact of the sacro-pubic region of the body being the chief focus of concealment proves the importance of this factor of modesty. But it may fairly be argued that it owes this position not merely to being the sexual centre, but also as being the excretory centre. Even among many lower mammals, as well as among birds and insects, there is a well-marked horror of dirt, somewhat disguised by the varying ways in which an animal may be said to define "dirt." Many animals spend more time and energy in the duties of cleanliness than human beings, and they often show well-marked anxiety to remove their own excrement, or to keep away from it.[35] Thus this element of modesty also may be said to have an animal basis. It is on this animal basis that the human and social fear of arousing disgust has developed. Its probably wide extension is indicated not only by the strong feeling attached to the constant presence of clothing on this part of the body,--such constant presence being quite uncalled for if the garment or ornament is merely a sort of sexual war-paint,--but by the repugnance felt by many savages very low down in the scale to the public satisfaction of natural needs, and to their more than civilized cleanliness in this connection;[36] it is further of interest to note that in some parts of the world the covering is not in front, but behind; though of this fact there are probably other explanations. Among civilized people, also, it may be added, the final and invincible seat of modesty is sometimes not around the pubes, but the anus; that is to say, that in such cases the fear of arousing disgust is the ultimate and most fundamental element of modesty.[37] The concentration of modesty around the anus is sometimes very marked. Many women feel so high a degree of shame and reserve with regard to this region, that they are comparatively indifferent to an anterior examination of the sexual organs. A similar feeling is not seldom found in men. "I would permit of an examination of my genitals by a medical man, without any feeling of discomfort," a correspondent writes, "but I think I would rather die than submit to any rectal examination." Even physicians have been known to endure painful rectal disorders for years, rather than undergo examination.