EFFECTS OF THALLIUM AND HAIR GROWTH IN RAT 133 48 hours previously. Mitotic activity has ceased in the bulb, and the cells are separating, indicating they are in a regressing condition. The effects of thallium upon the hair follicle on the fourth day following poisoning can be seen in Fig. 3. The papilla and connective tissue sheath show prominent deposits of alkaline phosphatase. The follicle is retracting outwardly with a few cells of unknown origin at the basal end of the hair. Figure 4, five days after administration of the thallium, shows the hair at the resting level. Residual cells and papilla at the base of the hair are surrounded by the connective tissue sheath in such a way as to keep the papilla intact with its hair. Five to six days after poisoning, the residual cells between the hair and papilla begin to increase and proliferate a new hair bud (Fig. 5). Figure 6 shows the proliferation more advanced and a very prominent papilla. The alkaline phosphatase reaction of the papilla and connective tissue •. • '•: -• .:- ..., .:}.: .::'Z .':,•o ,•:•. •:: 7.:' :•. :•'. ::.•' :. : .... -.• ::• ..• ..... :. ":•:• ... •.: '3 ß '2 .•'. . .:Z ..:'3• .• '•2-: ? '.'.'.' ... ½,&:.:: ::•.-•.., % :•'•:•3........ "' ........ -•.. ¾ .•, .:3: ..: .... .?½7: - -'• ... '• :.:..., •...• .' ß ß: ..• .,.:,.- -::. . E .½.., . Figure 8.--Succinic dehydrogenase in normal follicle 190X. Figure 9.--Great decrease of succinic dehydrogenase is shown in treated animal 190X. Figure 10.--Disulfides in follicle from a poisoned animal 190X. sheath enables one to follow them through the regression of the follicle and the start of proliferation for the next hair. These successive stages show that the papilla persists from one generation to the next generation as postulated by Wolbach (7). The history of the papilla of the normal hair (Fig. 7) can now be stated with certainty. To see if the distribution of succinic dehydrogenase would provide any information on how the thallium causes the cessation of growth, normal follicles and follicles from

134 JOURNAL OF THE SOCIETY OF COSMETIC CHFMISTS animals treated with thallium were studied. In the normal follicle, much activity is seen in the bulb (Fig. 8). In the follicles of the treated animal, there is a great decrease in the succinic dehydrogenase as is evident in Fig. 9. Whether the oxidative metabolism has been affected directly by the thallium or was reduced by death of the cells or cessation of mitosis cannot be determined by this technique. Glycogen is found in inactive epithelium. For instance, it is present in the prickle cell layer of the epithelium (8). In the normal hair follicle, it can be seen in the outer root sheath (Fig. 11). The greatest concen- tration is found in the middle third. The upper and lower thirds of the sheath are practically free from it. The derreal papilla contains no gly- cogen. Two to three days after poisoning the rat, the cells of the bulb are regressing and separating (Figs. 12 and 2). In Fig. 12 glycogen is very Figure 11.--Glycogen distribution in a normal follicle, p = papilla 180X. Figure 12.- Follicle is retracting, cells of bulb are degenerating and glycogen distribution is evident two days after poisoning, p = papilla 180X. Figure 13.- Outer root sheath with much glycogen remains below hair 180X. Figure 14.--Cells of outer root sheath are massed below hair as the residual cells, p = papilla 180X. Figure 15.--Glycogen has disappeared from residual cells. p -- papilla 180X. prominent in the outer root sheath, and the follicle is retracting outwardly. The hair continues to ascend, while basally there is some keratinization (Fig. 13). Figure 10 shows the extent of keratinization by the distribution of the disulfide groups. (Note the similarity in the extent and form of the keratinization in Figs. 10 and 13.) With the ascent of the hair, the outer epithelial root sheath cells, marked by their high glycogen content• remain