MILK-SUGAK. 295 



a product of combustion, which passes into the urine and renders 

 it alkaline. This experiment undoubtedly shows that the principal 

 metamorphosis of the sugar occurs primarily in the blood, and not 

 in the intestinal canal. 



That the sugar undergoes vinous fermentation in the intestinal 

 canal is a view that is now entirely rejected ; for the yeast-cor- 

 puscles which we sometimes find in the contents of the intestines, 

 and which might lead to the suspicion of such a fermentation, may 

 take their origin from the food, as, for instance, from bread. 



Does the sugar take any part in the formation of bile ? We 

 have already attempted (see p. 126 and p. 270) to show the proba- 

 bility that the bile is in part formed from fat, and that cholic acid 

 should be regarded as conjugated oleic acid with the adjunct 

 C 12 H 6 O 6 . Can this adjunct take its origin from the sugar ? 



Those who assume that sugar exists preformed in nitrogenous 

 animal substances, whether gelatinous or albuminous, (as for 

 instance it does in amygdakn,) need feel no difficulty in believing 

 that in the animal body protein is primarily formed from nitro- 

 genous matters and sugar. In the case of chitin, however, (to 

 which further reference will be made in a future page,) we appear 

 rather to have a combination of vegetable fibre with a nitrogenous 

 substance. 



We can hardly entertain a doubt that in the female mammalia 

 the milk-sugar is derived from the glucose, but by what means this 

 change is accomplished is a point on which we are entirely ignorant. 



MlLK-SuGAR. C 10 H 8 O 8 . 



Chemical Relations. 



Properties. This substance forms white, opaque, overlying 

 prisms or rhombohedra containing 2 atoms of water, is hard, 

 craunches between the teeth, has a very faintly sweet, almost 

 floury taste, is devoid of smell, dissolves slowly in cold but more 

 readily in hot water, and is insoluble in absolute alcohol and ether ; 

 the aqueous solution which moreover turns the plane of polarisation of 

 a ray of light to the right, may be evaporated to a very considerable 

 extent without any separation of the sugar in a crystalline form. 



When heated, milk-sugar melts, swells up, developes a sweetish 

 pungent odour, and burns with a flame. 



Digested with dilute sulphuric or hydrochloric acid, or with 



