SHEDDING OF SINUS HAIRS IS NOT SIMILAR TO SHEDDING OF PELAGE HAIRS - HISTOLOGICAL STUDY ON THE SINUS HAIR FOLLICLE OF THE CAT

Sinus hair and sinus hair follicle are considerably different from pel age hair and pelage hair follicle, especially as far as the structural features of hair shedding and hair cycle are concerned: 1. Sinus hair s are not subject to a seasonal hair shedding; they are shed continuou sly as single hairs. 2. A hair cycle occurs with a phase of growth, in volution, and rest, respectively. It is typical for the sinus hair fol licle that specific functional elements are not discharged, but remain as permanent structures: the blood sinus together with the entire con nective tissue root sheath, vast parts of the outer epithelial root sh eath, cells of Merkel included, both, the system of afferent and effer ent functional blood vessels, and nerve fibers. 3. The root of the sin us hair does not contain a medulla, but a highly vascularized ''connec tive tissue core''. 4. The new, outgrowing sinus hair grows into the c entral area of the old sinus hair root. In this histologic study, the respective features are presented in comparison with the pelage hair. The morphologic data are subject to a functional interpretation.