. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 3. Complex intercellular membranes between the cu- ticle cells. Fig. 4. Complex intercellular membranes between the Henle cells (inner root sheath). The dense, closely adhering membranes of the cuticular cylinder not only appear to form a barrier separating the domain of keratin formation (cortex) from the domain of trichohyaline formation (inner sheath), but appear also to prevent the cuticle itself from acquiring sufficient raw materials. For although syntesis is rapid in the cortex and the inner root shea
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 3. Complex intercellular membranes between the cu- ticle cells. Fig. 4. Complex intercellular membranes between the Henle cells (inner root sheath). The dense, closely adhering membranes of the cuticular cylinder not only appear to form a barrier separating the domain of keratin formation (cortex) from the domain of trichohyaline formation (inner sheath), but appear also to prevent the cuticle itself from acquiring sufficient raw materials. For although syntesis is rapid in the cortex and the inner root sheath, in the cuticle itself, synthesis is delayed until above the constriction of the follicle when a form of amorphous keratin with a high cystine content ap- pears. A discussion of the structure of keratin and tricho- hyaline will be found elsewhere in this volume (2). These two proteins are responsible for the hardened and fibrous texture of the cells of the hair and sheath which develops rapidly above the follicular constric- tion. Simultaneously with the development of these intracellular products the intercellular structures also undergo a remarkable development. Until this level the adhesive contacts have consisted simply of the two plasma membranes and the intervening cement layer of 120-150 A thick. As the cells of the cuticle and sheath fill with protein, the plasma membranes suddenly dilate to a distance of 300-400 A and a series of complex layers form between them (figs. 3 and 4). The nature and function of these intercellular layers are obscure; possibly they serve to hold to- gether the hardened cells. The dense layers (one in the sheath cells and two or three in the cuticle) may be deposits of an electron dense tanning agent in a pervading less dense cement of the type described below. In the cortex the membranes also dilate and finally become cemented together but we have not found a layered structure. This investigation has been supported by grants to the Chester
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