During late telogen to early anagen secondary hair germ is newly formed by the downgrowth of a clubbed column which is indistinguishable
from the bulge. Serial vertical sections demonstrated that the early anagen terminal hair follicle formed the new secondary
hair germ associated with a lateral protuberance of basaloid cells which could be considered as the bulge of the new hair
follicle. Interestingly, the arrector pili muscle bundle was divided into two branches, one inserted into the original clubbed
end and the other into this protuberance of the secondary hair germ. CAM5.2-reactive Merkel cells were present not only in
the clubbed ends of the old follicle but also in the protuberance of the new hair germ. The formation of the lateral protuberance
of the new hair germ preceded the appearance of CAM5.2-reactive Merkel cells in this location. Ks19.1 immunoreactivity was
observed from the clubbed end to the upper half of the new hair germ. These phenomena occurred in early anagen before the
club hairs were shed. It is postulated that the early anagen hair follicle formed the area within the new hair germ equivalent
to the bulge and Merkel cells either moved from the bulge of the old hair follicle or differentiated
de novo from immature epithelial cells. Merkel cells or their products in the bulge may serve as attractants for the readjusting
arrector pili muscle to anchor to the bulge of the new hair follicle.
Key words Merkel cell - Arrector pili muscle - Bulge - Early anagen