4 IMMEDIATE PRINCIPLES 



stituent of food. When boiled with dilute acids, cane sugar is converted into 

 dextrose and levulose. A similar change takes place in gastric digestion. 



FATS. 



Palmitin (C 3 H 5 (C 16 H 31 O) 3 O 3 ) and Stearin (C 3 H 5 (C I8 H M O) 3 O 3 ), 

 which in solution in olein constitute animal fat, are insoluble in water, soluble 

 iri hot alcohol, ether, chloroform, benzole, &c. Under the influence of super- 

 heated steam they are decomposed, taking up water and yielding glycerine 

 and Palmitic and Stearic acids respectively. (C 3 H 5 (C, 6 H 3 , O) 3 O 3 -f 3 H 2 O 

 = C 3 H 5 (H 3 ) O 3 + 3 Ci 6 H 32 O 2 .) A similar change takes place more 

 gradually under the influence of pancreatic secretion in the intestine, as well 

 as in presence of albuminous bodies in putrefaction. Alkaline palmitates and 

 stearates (Soaps) are obtained when fat is dissolved in potash or soda with the 

 aid of heat ; such soaps exist in bile. When fat becomes rancid, it not only 

 undergoes transformation into acids and glycerine, but takes up oxygen, in 

 consequence of which volatile and pungent acids belonging to the same series 

 (C n H 2n O 2 ), but containing less carbon, are formed. 



Palmitin fuses at 40 C., Stearine at about 60 C. According to the pro- 

 portion in which they exist in different kinds of fat, the fusing points of such 

 fats vary. Thus, \vhile beef fat fuses at 37 C., and contains three parts of 

 Stearin and Palmitin to one part of olein, human fat, which contains less 

 Stearin and relatively more olein, fuses at 25 C. Olein (C 3 H 5 (C 18 H 33 O) 3 

 O 3 ), is the fluid fat in which stearin and palmitin are dissolved. Olein solidifies 

 a few degrees above freezing point, and is more soluble than the other fats in 

 ether. Palmitic Acid (C 16 H 32 O 2 ) and Stearic Acid (C 18 H 3G O 2 ) are crystalline 

 bodies, chiefly distinguished from each other by their relation to heat, the 

 former fusing at 62 C., the latter at 70 C. Their relations to solvents cor- 

 respond with those of the fats. Palmitic acid crystallizes from its solution in 

 hot alcohol in bunches of fine needles ; stearin in shining plates. Oleic Acid 

 (C 18 H 34 O 2 ), which belongs to the series C u H 2n _ 2 O 2 , fluid at ordinary 

 temperatures, is decomposed by strong potash, potassic palmitate and acetate 

 being produced. 



Butyrine (C a H 5 (C 4 H 7 O) O 3 ) and the corresponding glycerides of other 

 volatile acids (capronic, caprylic, and myristinic) occur in small proportion in 

 butter. 



FOOD. 



F/esfrowes its nutritive value to its albuminous and colla- 

 genous constituents, its fat and its salts. Lean meat (beef) 

 contains about 25 per cent, of solids, of which 18 percent, 

 is albumin, and yields about 2 per cent, of gelatin to 

 boiling water. Flesh of young animals (veal) yields 5 to 

 10 per cent. The interstitial fat of meat varies in quantity 

 from 4 to 1 5 per cent. 



