Figure 1-2. The early stages in the development of the hair follicle and hair. Each hair is formed in a follicle which arises embryologically as a thickening and inpushing of the epidermis. Subsequently, the base of the follicle thickens forming a cylinder on top of a papilla of mesodermal origin. By multiplication of this matrix of epidermal cells the hair shaft is formed, while the outer wall of the follicle forms a sheath round the base of the hair. Based on Searle ( 1968a).