158 



M. S. C. BIRBECK AND E. H. MERCER 



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 Beatty Research Institute (Institute of Cancer 

 Research: Royal Cancer Hospital) from the British 

 Empire Cancer Campaign, Jane Coffin Childs Memorial 

 Fund for Medical Research, the Anna Fuller Fund, and 

 the National Cancer Institute of the National Institutes 

 of Health, U.S. Public Health Service. 



The authors are particularly grateful to Mr. K. G. 

 Moreman for supplying the illustrations. 



References 



BiRBECK, M. S. C. and Mercer, E. H., E.xptl. Cell 



Research 10, 505 (1956). 

 — These Proceedings, p. 159. 



Palade, G. E., /. Biophys. Biocheni. Cytol. 1, 567 (1955). 

 ScHMiTT, F. O., Growth 5, 1 (1940). 

 Waddington, C. H., Principles of Embryology. Allen & 



Unwin, London, 1956. 

 6. Weiss, P., /. Embryol. E.xptl. Morphol. 1, 182 (1943). 



Electron Microscopic, X-Ray and Birefringence Studies 

 on the Proteins of the Hair Follicle 



M. S. C. BiRBECK and E. H. Mercer 



Chester Beatty Research Institute, Institute of Cancer Research: 

 Royal Cancer Hospital. London, S. W. 3 



(^ells derived from the mammalian epidermis are 

 able to synthesise a variety of materials some of 

 which are fibrous. In the hair follicle (fig. I), for 

 example, two very different fibrous products appear, 

 trichohyaline and keratin. The formation of these 



substances can be followed in the polarisation and 

 electron microscopes and to a limited extent by 

 means of x-ray diffraction. The hair follicle therefore 

 provides an excellent opportunity for correlating 

 the results of the three techniques. 



