100 MILK 



ferences in rotation, but that error is Ukely to occur because the 

 rotation of lactose varies under different conditions. If, for 

 example, lactose has been desiccated before dissolving, or if the 

 solution stands for some time, the rotation may vary 100 per 

 cent, either way. Furthermore, when a solution of lactose is 

 heated to 120°-130° C. in the presence of alkali, sodium phos- 

 phate, or casein substances are formed which have lower rotation 

 than lactose, but similar reducing power. 



Theobald Smith concluded from observations of bacterial 

 activity that milk contains 0.1 per cent, of a, carbohydrate which 

 is similar to dextrose. On the other hand, Leichmann has shown 

 that Bacillus delbriicld, a bacillus of the group of lactobacilli, 

 produces no fermentation in milk, although it decomposes dex- 

 trose, but not lactose. 



These experiments were made in cow's milk. Pdchmond 

 found a carbohydrate in the milk of the gamoose or Egyptian 

 buffalo and named it "tewficose." This same author states that 

 mare's milk easily undergoes alcoholic fermentation, a property 

 not possessed by lactose. However, investigations by Hastings 

 have shown that lactose-fermenting yeasts are widely distributed 

 and, therefore, fermentation of milk can easily occur if conditions 

 are favorable. Richmond also states that experiments made by 

 Carter and himself seemed to show that the milk-sugar in human 

 milk is not identical with that of cow's milk. 



At the present time it is impossible to decide whether car- 

 bohydrates — other than milk-sugar — really occur in milk. If 

 they do, they are present in small quantity only and probably 

 have no significance. Milk-sugar prepared from the milk of dif- 

 ferent animals has the same properties. 



Milk-sugar is not as readily soluble in water as other sugars. 

 Solutions of lactose are, therefore, not as sweet as solutions of 

 cane-sugar or dextrose. Milk-sugar is soluble in about 6 parts 

 of cold water and in 2^ parts of hot water. Milk-sugar crystal- 

 Kzes in rhombic prisms from a concentrated solution, leaving a 

 mother liquor which contains 21 per cent, of sugar. The crystals 

 contain one molecule of crj^stallization water. To prepare milk- 

 sugar on a large scale whey is evaporated to a syrupy consistency 

 and crystals are allowed to form. These are redissolved, the solu- 

 tion decolorized with animal charcoal, and recrystallized. It is 

 usually sold in a white, slightly sweetish powder, and is used as a 

 vehicle for drugs and for modifying milk for infant feeding. 



Milk-sugar exists in several modifications. The hydrated «- 

 milk-sugar crystallizes from water and has a high rotation which 

 diminishes when the solution stands for some time. Anhydrous 

 milk-sugar is obtained when a sugar is heated to 130° C. It is 



