270 



KERATIN AND KERATINIZATIOM 



of rabbit fur (Table 20). The cystine content is very low, citruiline is 

 present and half the side chains are either acidic or basic. It thus appears 

 quite distinct from other hard keratins and resembles trichohyalin. 



Table 20. Composition of Rabbit Fur 



and Medulla.* 



(N as per cent of total-N.) 



* Taken from Rogers (1959a). 



t The presence of citruiline may prove to be diagnostic of tricho- 

 hyalin. 



The residues remaining after the chemical extraction of 

 keratins 



Much has been learned concerning the chemical nature of the con- 

 stituents of keratinized tissues by scrutinizing the residues which remain 

 after subjecting the tissue to the treatments described above designed to 

 remove definite components. For example, the extraction of the proteins, 

 which become soluble after complete disulphide-bond destruction, enables 



