LECTURE II. 



CARBOHYDRATES. 1 

 I. 



IN GENERAL MONOSACCHARIDES GLUCOSAMINE GLUCURONIC 



ACID. 



THE carbohydrates are extremely abundant in nature. They take a 

 prominent share in the building up of the vegetable kingdom, and play an 

 important part as food in animal economy ; while on the other hand, com- 

 pared with the protein bodies, they scarcely come into consideration at all 

 as building materials for the animal tissues and cells. The most important 

 representatives of this class of bodies have been known for a long time, 

 especially cane sugar, which before the beginning of the Christian era was 

 obtained in India in a solid form by boiling down the juice of the sugar- 

 cane. To-day, besides the sugar-cane, the sugar-beet 2 forms an important 

 raw material. Again, grape-sugar has been known for a long time, and 

 was first discovered in honey although prepared pure for the first time 

 by Marggraf in the middle of the eighteenth century. In the year 1615 

 Bartolleti 3 isolated a third member of this group from milk, namely 

 milk-sugar. If we add to these cellulose and starch we have named 

 all of the members of the carbohydrate group which were known up to 

 the time that the study of organic chemistry as we know it to-day began 

 as a result of the experiments of Lavoisier and Scheele. If we disregard 

 a few isolated although very important observations e.g., Kirch- 

 hoff's discovery that starch was changed into grape-sugar by boiling with 

 dilute acids, 4 and that the same process could be brought about by a sub- 

 stance found in grain or malt 5 very little was known in chemistry, 

 and consequently in physiology, concerning carbohydrates up to within 

 very recent times, and this period of darkness disappeared only with the 

 important investigations of Kiliani and of Emil Fischer especially. 



1 The following references cover this field: Emil Fischer: Ber. 23, 2114 (1890). 

 E. 0. V. Lippmann: Die Chemie der Zuckerarten (1904). B. Tollens: Kurzes 

 Handbuch der Kohlehydrate (1898). 



3 Discovered by Marggraf (1747); Ber. Berlin. Akad. Wissensch. 79, 1749. 



3 Encyclopaedia dogmatica, 1615. 



4 J. d. Pharm. 74, 199 (1811). 



5 Schweigger's J. 14, 389 (1814). 



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