On Symmetrical Thinness of the Parietal Bones

Royal College of Surgeons' Museum, Edinburgh. The occurrence of bilateral thinness of the parieta ones been recognised for many years. Numerous records o 1 ocjc" within the past century but the explanations of it stil ai satisfy. It has been written of as a senile atrop y, as an atrophic condition not necessarily senile, as a congenita e e , as the result of muscular action, and even as o trauma origin. I hope to show that a more universally applicao explanation, one that suits every case and any degree, is a dysplasia of the diploe. There is no question of inJ^' evidence of an inflammatory process; symmetrica ?ccurs in individuals who are neither senile in year senile in body, and its absence in childhood makes t ie " congenital " equivocal. This condition is often spo "symmetrical thinning," ^^.^^^P^^ness6which is Participle presupposes an earlier degree of -n Undergoing progressive diminution. My conten ion never ^e centre of the affected parietal area the ip oe same developed, and this part of the parietal has remaine where c?ndition as the lower parts of the inferior occipi a j;0i0e "1 'he bone is "thin, semi-transparent and dest.tuK-. of *pU> It is, to use a word coined by Sir Will.am Gowers^^ ^ "Produced by Keith,38 an abiotrophy, an i P ^ of apparent congenitally but becoming so u Involuntionskrankpowth. Such a conception invalidates iye of atrophy eit of Virchow2 and all exPresslons