PubMed · 281890
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F F Crutcher. 1978. Protrusion.. https://doi.org/10.1043/0003-3219(1978)048%3C0324%3Ap%3E2.0.co%3B2
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Gene frequencies for 13 marker systems are used to construct synthetic gene frequency maps of South America. The surfaces generated using the first three principal components exhibit clines which validate models of population displacement based on archeological data and a previous analysis of craniometrical variation.
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The development of the paranasal or accessory sinuses begins very early in utero. In the newborn the ethmoidal sinus, which gives rise to all the other sinuses, as well as the maxillary sinus, can already be identified on x-rays. The frontal sinus appears as a triangle at the age of four and oversteps the supraorbital margin at the age of six. The sphenoidal sinus begins to excavate the concha sphenoidalis at the age of four and can be seen on x-rays at the age of eight, when it extends to the hypophyseal fossa. In the twelve-year-old child all sinuses almost reach their final sizes. However, the size and shape of all sinuses, particularly of the frontal and the sphenoidal sinuses are very different.