VESTIGIAL ORGANS
to cut the gums are, strictly speaking, vestigial organs, for under such conditions they are absolutely useless.
Not only is man the possessor of numerous vestigial organs in his adult state, but he also exhibits organs of this kind in his early stages of growth. Just within each nostril of the human embryo, or even of the new-born babe, is a small pore on the median wall of the nasal chamber (Fig. 8).
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This pore leads into a short, blind tube in the nasal wall. The pore and tube occupy exactly the position of Jacobson’s organ of the lower vertebrates. This organ is an accessory organ of smell, which is well developed in many mammals and other vertebrates. In vertebrates other than man Jacobson's organ is provided with branches from the olfactory nerve, the nerve of smell, but in man this innervation is said to be lacking. As the organ disappears in man with the passing of childhood, and as it never shows signs of functional activity, it may be recorded as a vestigial organ of embryonic and early post-natal life. Another vestigial feature, prenatal in time of occurrence, is seen in the lanugo of the human embryo, the covering of fine woolly hair found on the skin of the unborn human infant. This hairy covering is ordinarily shed before birth, and the separate hairs may often be identified in the amniotic liquor in which the embryo is immersed. This hairy covering is like that of the foetus of most mammals. At no time can it be of functional importance to the human embryo,
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