ii PRIMARY DISSOCIATION-PRODUCTS 61 



lactic acid to be a primary dissociation -product of albumin (see 

 p. 83). 



Keratines are richest in sulphur and cystin. From horn filings 

 Morner obtained 6*8 per cent, from human hair 13 '92 per cent, and these 

 figures are certainly too low, as they only express minimal estimates. 

 Other albumin substances contain much less : serum-albumin 2*5 per 

 cent, and casein and egg-white only traces. 



Patten J and Rothera, 2 on using Hopkins' and Cole's acid mercuric 

 sulphate reagent, 3 obtained from hair only 4 per cent of cystin in the 

 shape of hexagonal crystals. Rothera states that there is no difference 

 between stone or calculus cystin and that prepared by hydrolysis of hair. 

 As he noticed a violet colour-reaction by the simultaneous use of ferric 

 chloride and ammonia, which Morner believes to be characteristic of 

 a-thiolactic acid, and as the latter is a derivative of a-thio-/2-amino- 

 glyceric acid, it follows that stone-cystin is decomposed by the mercuric- 

 sulphate method, while protein-cystin is not, for the latter Rothera 

 obtained in the typical hexagonal plates. It must also be borne in 

 mind that all cystin stones are not composed of stone-cystin, for 

 which reason the expression ' stone-cystin ' is not a very appropriate 

 one. It is for this reason that the author suggests to call the protein- 

 cystin, A-cystin ; and the stone-cystin, B-cystin. 



The second paper by Neuberg and Mayer and that of Gabriel 

 were alluded to at the beginning. 



PHYSIOLOGICAL CONSIDERATIONS. Cystin, according to Wohlge- 

 muth, 4 is the principal, if not the only, mother substance of the 

 sulphates, the unoxidised sulphur and the 'salts of dithionic acid 

 (H 9 S 9 6 ) 5 in the urine ; further, of the taurin of bile, and also of the 

 products of intestinal decomposition, namely, hydrogen sulphide, H 9 S ; 

 methyl-mercaptane, CH 3 . SH, and ethyl-sulphide, (C 2 H 5 ) 2 . S. Wohlge- 

 muth 6 has shown experimentally that feeding rabbits with cystin leads 

 to an increased production of taurin, and partly also to the formation 

 of taurocholic acid in the bile. 



During cystinuria, which depends on a disturbance of the amino- 

 acid-metabolism, ty rosin, leucin, aspartic acid, and cystin are not dis- 



1 A. J. Patten, Zeitschr. f. physiol. Chem. 39. 350 (1903). 



2 C. H. Rothera, Journ. of Physiol. 32. 175 (1905). 



3 Hopkins and Cole, ibid. 27. 421 (1902). 



4 J. Wohlgemuth, Verhand. d. Gesellsch. deutsch. Naturf. u. Arzte, 1903, p. 423, 

 -and Zeitschr. f. physiol. Chem. 40. 81 (1903) ; ibid. 43. 469 (1905). Here also the 



older litteration is dealt with. 



5 Dithionic acid decomposes according to the equation H 2 S 2 6 + H.,0 = H 2 S0 3 + H 2 S0 4 . 

 No sulphur separates out. 



6 J. Wohlgemuth, ibid. 40. 81 (1903). 



