The Structure and Chemistry of Human Hair 18 hairs.39 In stick-straight hair, such as from Japanese, the entire cross-section was occupied by cortical cells of the para-type. In lightly curly hairs from Europeans most of the section was occupied by cells of the para-type but with a rim of one or two cells depth of the ortho-type. These latter cells were adjacent to the cuticle at one end of the minor axial diameter of the elliptical transverse fiber section. In intensely curly hair of African origin cells of the ortho- and para-type were divided more-or-less evenly about the major axial transverse diameter. This work also revealed the orthocortical segments in curly hairs of African and European origin were invariably located on the end of the minor axial diameters towards the outside of the curl for points along the hair. In consequence when curly hair is pulled straight, the orthocortical segment at one end of the minor axial diameter rotates along the length of the hair. The general conclusions of these early studies have been confirmed recently and considerably amplified in their detail, particularly with respect to the types of proteins found in the different cortical cell types.40-45 Cells of a third type have been identified in the human Figure 9. Intermediate magnification transmission electron micrographs of a transverse section of human hair stained with ammoniacal silver nitrate. The left picture is of a region designated as paracortex and the right picture is of orthocortex. Note the differences in packing of the keratin macrofibrils between the two cell types.