[Anatomy of the upper and lower lips between the 4th intrauterine month and labor].
Report on the histological development of the lips between the 4th and 10th month of intrauterine life with a survey of the literature. It is proposed to classify the different segments of the lip into 5 zones: Pars cutanea--Pars glabra--Pars intermedia--Pars villosa--Pars mucosa. Special interest is given to the arising of the papillae which are first to be seen around the 4th month. From the 8th month forward, they become villi which rise above the surface of the epithelium. Due to proliferation of the epithelium there is found between the 4th and 7th month a torus at the end of the Pars Villosa which ought to be named "Torus labialis internus". Beside this a so called "Torus labialis externus" is described stipulating the typical doublelip of the newborn infant. The function of the villi is discussed in connection with the bloodvessels. Because of their number and location there is likely to be a swelling-function of the lips. Finally a case is presented dealing with a sebaceous gland in the Pars mucosa.