MONOSACCHARIDES IN LIVING TISSUES 69 



basic acid derivative of an aldohexose is acted upon by oxidizing agents, 

 the carboxyl group is eliminated in the form of carbon dioxide and 

 water, and the corresponding aldo-pentose is formed. When d-glucu- 

 ronic acid is subjected to intense putrefaction, it undergoes an analogous 

 change, with the production of 1-xylose, thus : 



CHO CHO 



I I 



H C OH . H C OH 



I I 



HO C H HO C H 



+ CO 2 

 H C OH H C OH 



H C OH CH 2 OH 



COOH 



Glucosamin, on the other hand, affords a connecting link between 

 the carbohydrates and the hydroxy-amino-acids. It is readily obtained 

 in considerable quantities from the exoskeletons of Crustacea, as for 

 example from the shells of lobsters, by boiling with concentrated 

 hydrochloric acid. It also occurs in fungi and it is a constituent of the 

 Mucins and Mucoids; sticky glutinous proteins which are found in 

 mucous secretions and elsewhere. The formula of glucosamin is: 



CHO 



H C NH 2 

 HO C H 

 H C OH 

 H C OH 

 CH 2 OH 



In the true mucins, but not in the mucoids the glucosamin radical is 

 probably acetylated, and acetyl glucosamin, in common with other 

 acetyl derivatives of hydroxy-amino-acids, yields Ehrlich's Reaction, 

 namely a pink color when its solution is mixed and warmed or allowed 

 to stand with an equal volume of a two per cent, solution of paradi- 

 methylaminobenzaldehyde in hydrochloric acid of specific gravity 

 1.09. The mucins also yield this reaction. 



THE DISTRIBUTION OF THE MONOSACCHARIDES IN LIVING 



TISSUES. 



As has been stated, a pentose, d-Ribose is a normal constituent of 

 the nucleoproteins. The following, after Grund, is the percentage 



