Plate 16 



Cross-section of fibrous keratin in the cortex of the fully-hardened 

 wool fibre. Portions of several fibrils are seen with an almost effaced 

 interfibrillar line at (I). At R are seen residues of cytoplasmic debris. 

 The material consists of close packed filaments embedded in a ground 

 substance (matrix), which is denser after reaction with the osmium fixative 

 than the filaments themselves. At H an almost perfect hexagonal packing 

 is visible. For an interpretation of the pattern see Figures in text. Com- 

 pare with the less well-oriented material found in skin keratin shown in 

 Plate 17. Magnification X 100,000. 



Photograph kindly lent by Dr. G. E. Rogers. 



