THE KERATINIZATION PROCESS 



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parallel arrangement of long, thin rodlets, with or without internal 

 anisotropy, when immersed in a medium of a different refractive index 

 (Schmidt, 1924; Schmitt and Bear, 1939). Experimentally the dis- 

 tinction is made by observing the change in the birefringence due to form 



Fig. 91. The development of orientation and its stability. X-ray patterns 

 obtainable from the different levels are shown diagrammatically. The 

 a-pattern is obtained immediately above the bulb in zone D but on 

 warming the unstabilized fibre is disoriented and yields an unoriented 

 /3-pattern. In the zones E and F the pattern is stable to heating below 

 100° C. On the right-hand side is shown the birefringence (An) in the 

 cortex and the levels (zone D shown clear) where it is destroyed by heat. 



when fluids of different refractive index are allowed to penetrate the object. 

 Unfortunately this method is inapplicable to the hard keratins, such as 

 hair, since by the very process of keratinization the material has become 

 impervious to liquids which do not cause far-reaching disintegration 

 (Barnes, 1933; Mercer, 1949). For this reason the clearest understanding 

 of orientation phenomena comes from X-ray diffraction. 



