CARBOHYDRATES. 35 



union is possible only after the animal organism itself has produced some 

 change in the objectionable substance. 1 



Quite different from glucuronic acid in its properties is the compound 

 d-glucosamine, also known as chitosamine. It was first prepared in large 

 amounts from the chitin of lobster shells, 2 and later, as has been mentioned, 

 from mucin substances and as a cleavage product of proteins. The con- 

 stitution of glucosamine has been recently cleared up by Fischer and 

 Leuchs. 3 It is to be regarded as a derivative of either d-glucose or d- 

 mannose, in which the hydroxyl of the a position is replaced by the amido 

 group, NH2- Its configuration is the following: 



H H OH 



I I I 



CH 2 (OH) C - C C --CH(NH 2 ) . CHO 



H 



OH 01 



Glucosamine is a very interesting compound. It forms an intermediate 

 step between the hexoses and the hydroxy-a-amino acids, which we will 

 soon meet with as cleavage products of the proteins, so that glucosamine, 

 in a sense, forms a bridge between the proteins and the carbohydrates. 

 At present we know nothing concerning the physiological significance of 

 glucosamine. It does not occur free in the above-mentioned substances, 

 but in a polymeric form either alone or with other sugars. 



Finally there remains one other amino-sugar to mention which we have 

 already touched upon, namely, galactosamine. It was discovered by Schulz 

 and Ditthorn and represents a component of the glucoproteids in the albu- 

 minous gland of the frog. Its constitution is not known at present. 



1 Cf. Fromm's Die chemischen Schutzmittel des Tierkorpers bei Vergiftungen, Strass- 

 burg, 1903. 



2 Ledderhose: Z. physiol. Chem. 2, 213 (1878-79); 4, 139 (1880). H. Steudel: ibid. 

 34, 353 (1902). 



3 Ber. 35, 3787 (1902); 36, 24 (1903). 



