38 LECTURE III. 



as maltose. Emmerling 1 showed, however, that isomaltose was chiefly 

 present in this case. Later on we shall take up the syntheses produced 

 by the action of ferments more in detail, as well as their biological impor- 

 tance. 2 



Isolactose occupies a quite similar position, and has been obtained by 

 Fischer and Armstrong 3 from a mixture of d-glucose and d-galactose under 

 the influence of lactoglucase. 



Cane-sugar, also known as sucrose, saccharose, and saccharobiose, is of 

 great importance for plant and animal organisms. 4 It plays an important 

 part in the reserve-stores of all Phanerogamia, and is found chiefly in 

 tissues containing no chlorophyll, although it is present in smaller quan- 

 tities in all parts of the plant. It occurs to the greatest extent in the 

 stalk of the sugar-millet (sorghum) and sugar-cane, in the sap of certain 

 kinds of palm, that of the sugar-maple, the birch and the carob tree (St. 

 John's bread). Considerable amounts are found in the ripe fruits and 

 leaves of various growths. At present the sugar-beet is cultivated exten- 

 sively on account of the cane-sugar it contains, and, together with the 

 sugar-cane, forms the source of practically all commercial sugar. 



This important food and condiment has never been positively identified 

 in the animal organism. It is certain that it takes no part in intermediary 

 metabolism. This follows from the fact that cane-sugar introduced into 

 the veins is not utilized, but passes off unchanged in the urine. In order 

 for this sugar to be of value to the animal organism, it must first be 

 subjected to hydrolysis in the digestive tract. 5 



Cane-sugar, as proved by Liebig in the year 1834, corresponds in its 

 composition to the formula C^B^On. It decomposes under the action 

 of hydrolytic agents into one molecule of d-fructose and one of d-glucose. 

 Since the d-fruetose in this mixture rotates the plane of polarized light more 

 to the left than d-glucose does to the right, the product is Isevorotary, that 

 is to say, in the opposite direction as compared with cane-sugar, which is 

 strongly dextrorotary. For this reason this mixture of equal parts of the 

 two hexoses obtained by the cleavage of cane-sugar is called invert-sugar, 

 and the process is spoken of as inversion* Its formation was first studied 

 by Dubrunfaut 7 in 1830. Mixtures of fruit- and grape-sugars, moreover, 

 occur very extensively in nature (honey, fruit, etc.). 



1 Ber. 34, 600 and 2206 (1901). 



2 See lecture on Ferments. 



3 Ber. 35, 3144 (1902). 



4 E. Schulze and S. Frankfurt: Z. physiol. Chem. 20, 511 (1895). 



5 Claude Bernard: "Lemons sur le Diabete," p. 249 (1877). Fritz Voit: Deut. Arch, 

 klin. Med. 68, 523 (1897). 



6 This term is also used in general to denote the hydrolytic decomposition of com- 

 pound carbohydrates into simple sugars. The opposite change is called reversion. 



7 Compt. rend. 25, 308 (1847); 29, 51 (1849); 42, 901 (1856). 



