114 



THE PROTEIN SUBSTANCES. 



of tyrosine. It is remarkable that the egg membrane of the Selachii, 

 which biologically is analogous with ovokeratin, differs from the typical 

 keratins by the absence of cystine, while it contains, on the contrary, 

 large amounts of tyrosine. The typical keratins differ among them- 

 selves in regard to composition, thus the keratin from the sheep hoofs 

 contains 2 per cent phenylalanine while this amino-acid is absent in the 

 keratin of hair and feathers. It is difficult to say whether or not this 

 is due to a difference in the purity of the bodies or not. The keratins 

 as thus far investigated do not chemically form a sufficient characteristic 

 group. 



1 Abderhalden and Wells, Zeitschr. f. physiol. Chem., 46. 



2 Buchtala, ibid., 52. 



3 Argiris, ibid., 54. 



4 Abderhalden and Voitinovici, ibid., 52. 



5 Abderhalden and Le Count, ibid., 46. 



6 Abderhalden and Ebstein, ibid., 48. 



7 Korner, ibid., 34 and 42. 



8 Pregl, ibid., 56. 



9 Abderhalden and Strauss, ibid., 48. 



10 Abderhalden and Fuchs, Zeitschr. f. physiol. Chem., 57, have recently shown that 

 the same variety of keratin, on ageing of the horn structure, becomes somewhat poorer 

 in glutamic acid. 



Bodies occur in the animal kingdom which form to a certain extent 

 intermediate substances between coagulated protein and keratin. C. 

 TH. MORNER l has detected such a body (albumoid) in the tracheal car- 

 tilage which forms a net-like trabecular tissue. This substance appears 

 to be related to the keratins on account of its solubilities and the quan- 



1 See Maly's Jahresber., 18. 



