THE KERATINIZATION PROCESS 



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the cornified keratin which thus may be regarded as a mixture. This view 

 is supported in part by the superb micrographs of Brody (1959) (Plate 17) 

 which show that the keratin of the epidermis has essentially the same fine 

 structure as the hair cortex: poorly-stained filaments embedded in a 

 strongly-stained matrix. The filaments here are not strictly parallel as in 



iiiii 



Fig. 99. Schematic drawing of the upper part of the epidermis (guinea- 

 pig) taken from Brody (1959). The fully-keratinized cells contain the 

 typical keratin pattern of unstained filaments embedded in a stained 

 amorphous matrix as illustrated in the electron micrographs (Plate 17). 

 In the stratum spinosum S tonofibrils predominate, in the granular layer 

 G filaments and granules K of keratohyalin are present. The curious 

 association of granules and filaments is suggested at T. In the trans- 

 itional cell, which follows, the cytoplasm is more condensed, the cell 

 boundaries more dense and keratohyalin predominates. The dense 

 particles P still persist. 



hair cortical keratin; they cluster in somewhat wavy bundles lying more 

 or less in the plane of the flattened cell. Brody suggests from the juxta- 

 position of granules and filaments in the stratum granulosum that the 

 keratohyalin granules " incorporate " the filaments (Fig. 99). He thus 

 derives the interfilamentous cement from the keratohyalin and on the 

 analogy with the work on the cortex supposes that this material must be 

 rich in cystine. He cites in support the finding of Chevremont and 



