8 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS SLIDE 7 Papillary capillaries and subpapillary plexus (after Spalteholz.) From Mfiller (•.09). (Reproduced by permission of F. Enke.) SLIDE 8 A schematic representation of the structural pattern of the capillary bed. The distribution of smooth muscle is indicated in the vessel wall. From Zweifach (•.99). (l•eproduced by permission of the Josiah Macy, Jr., Foundation.)

THE STRUCTURE OF SKIN 9 produces heat. Following the appearance of the line a red flare develops on either side of it, and, three minutes after the appearance of the flare, the reddened area begins to swell and forms a wheal which is pale in colour. These three reactions: red line, flare, and wheal represent the well-known triple response of skin. The wheal is caused by the leakage of blood plasma outside the vessels. It may last for as long as two hours. Emotional disturbances can cause changes in the appearance of the skin. Some years ago a medium was known who, in an hysterical trance, was able to reproduce on her forehead, hands and feet marks which looked as though they could have been made by a crown of thorns and by the nails used to fasten feet and hands in crucifixion. The skin is also affected by thermal stimuli and by the male and female sex hormones and, in fact, the perfect female complexion so sought after by cosmeticians for older women is produced in the young by the right balance of these two hormones. It is of interest that other steroid hormones do not affect the skin. The normal colour of the skin is determined partly by the amount of l..:',a. nd distribution of pigments in the epidermis and partly by the state of NORMAL HYPER-R[ ACTIV• HYPO-RE•TIV• SLIDE 9 Diagram of fluid exchange between blood and tissues. The number of stippled cells in the side branch indicates the number of open capillary channels. The arrows indicate the preponder- ance of fluid movement, the length of the arrow giving an approximation of the magnitude of fluid movement in com- parison to other capillary vessels. From Zweifach (299). (Reproduced by permission of the Josiah Macy, Jr., Founda- tion.)