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philtrum
The philtrum ((ラテン語:philtrum), (ギリシア語:φίλτρον) ''philtron''), or medial cleft, is a vertical groove in the middle area of the upper lip, common to many mammals, extending from the nose to the upper lip. Together with a glandular rhinarium and slit-like nostrils, it is believed to constitute the primitive condition for mammals in general.〔(Orders PRIMATES & SCANDENTIA )〕
==Function==
In most mammals, the philtrum is a narrow groove that may carry moisture from the mouth to the rhinarium or nose pad through capillary action, to keep the nose wet. A wet nose pad is able to trap odor particles better than a dry one, thus it greatly enhances the function of the olfactory system.
For humans and most primates, the philtrum survives only as a vestigial medial depression between the nose and upper lip.〔(Philip Hershkovitz,''Living New World monkeys (Platyrrhini): with an introduction to Primates'', University of Chicago Press, 1977, Vol. I, p. 16 )〕
The human philtrum, bordered by ridges, also is known as the ''infranasal depression'', but has no apparent function. That may be because most higher primates rely more on vision than on smell, and so no longer need a wet nose pad or a philtrum to keep the nose pad wet. Strepsirrhine primates, such as lemurs, still retain the philtrum and the rhinarium, unlike monkeys and apes.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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