THE CHEMICAL CONSTITUTION OF ITS UNITS 77 



carbohydrate has been obtained from carefully purified proteins contain- 

 ing no prosthetic group, such as crystallised egg-albumin, serum-albumin 

 (Langstein). The fact that the yield of carbohydrate from such a pro- 

 tein becomes smaller the more often it is recrystallised, suggests that 

 the presumably pure protein still contained an impurity; this impurity 

 would be a glucoprotein, which is found in both egg white and serum 

 from which the crystallised proteins are separated, and this would give 

 rise to the carbohydrate. 



The constitution of glucosamine, which has been synthesised by 

 Fischer and Leuchs, therefore forms part of the subject of glucoproteins. 



The constitution of all the amino acids except diaminotrioxy- 

 dodecanic acid is thus known, and with the exception of histidine they 

 have all been synthesised. The separation of the synthetical com- 

 pound into its optical antipodes has still to be effected in the case 

 of several of the amino acids. 



A brief summary of the discovery of the above ' amino acids and by 

 whom they were first synthesised is given in Table A. Table B con- 

 tains the specific rotatory powers of the natural and synthetical sub- 

 stances. 



