86 PROXIMATE PRINCIPLES OF THE SECOND CLASS. 



QUANTITY OF SUGAR IN 100 PARTS IN 



Figs .... 62.50 Wheat flour. . 4.20 to 8.48 



Cherries . . . 18.12 Rye meal . .3.28 



Peaches . . . 16.48 Indian meal . 1.45 



Tamarinds . . . 12.50 Peas . . . 2.00 



Pears .... 11.52 Cow's milk . . 4.77 



Beets .... 9.00 Ass's milk . . 6.08 



Sweet almonds . . 6.00 Human milk . 6.50 



Barley meal . . . 5.21 



Besides the sugar, therefore, which is taken into the alimentary 

 canal in a pure form, a large quantity is also introduced as an in- 

 gredient of the sweet-flavored fruits and vegetables. All the 

 starchy substances of the food are also converted into sugar in the 

 process of digestion. Two of the varieties of sugar, at least, 

 originate in the interior of the body, viz., sugar of milk and liver 

 sugar. The former exists in a solid form in the substance of the 

 mammary gland, from which it passes in solution into the milk. 

 The liver sugar is found in the substance of the liver, and almost 

 always also in the blood of the hepatic veins. The sugar which is 

 introduced with the food, as well as that which is formed in the 

 liver, disappears by decomposition in the animal fluids, and does 

 not appear in any of the excretions. 



3. FATS. These substances, like the sugars, are derived from 

 both animal and vegetable sources. There are three principal 

 varieties of them, which may be considered as representing the 

 class, viz : 



Oleine = C 94 H 87 15 



Margarine = C 76 H 75 12 



Stearine = C, 42 H 141 1T 



The principal difference between the oleaginous and saccharine 

 substances, so far as regards their ultimate chemical composition, 

 is that in the sugars the oxygen and hydrogen always exist together 

 in the proportion to form water ; while in the fats the proportions of 

 carbon and hydrogen are nearly the same, but that of oxygen is 

 considerably less. The fats are all fluid at a high temperature, but 

 assume the solid form on cooling. Stearine, which is the most 

 solid of the three, liquefies only at 143 F. ; margarine at 118 F. ; 

 while oleine remains fluid considerably below 100 F., and even 

 very near the freezing point of water. The fats are all insoluble 

 in water, but readily soluble in ether. By prolonged boiling in 

 water with a caustic alkali, they are decomposed, and as the result of 

 the decomposition there are formed two new bodies ; first, glycerine, 



