CH. VII.] BREAD 175 



dough to become hardened by coagulating the proteins. 

 It also converts starch into soluble starch and dextrin, thus 

 forming the crust. The brown appearance of this is due 

 to the conversion of glucose into caramel. 



211. Take a piece of the crumb of a stale .white loaf, rub it 

 up finely and pound with cold water in a mortar. Strain and 

 squeeze through muslin. A white fluid is obtained containing 

 wheat starch grains. Filter the fluid. To a portion of the filtrate 

 add a little Fehling's solution and boil : a well-marked reduction 

 occurs due to the presence of glucose. To another portion add 

 iodine : a purple colour is produced, showing the presence of erythro- 

 dextrin. If very dilute iodine be cautiously added, a blue colour 

 is produced at first, showing that a small amount of soluble starch is 

 present. 



Boil a small amount of the residue of the bread with water in a 

 beaker, strain through muslin and filter. Cool and test the filtrate 

 for starch and dextrin. (Ex. 145 to 147.) 



212. Repeat the above exercise, using the crust of bread 

 instead of the crumb. Note that glucose is absent or present in 

 traces only : dextrin and starch are present, a considerable portion 

 of the latter existing as soluble starch and being present in the cold 

 water extract. 



G. Meat (Muscle). 



The most important constituents of living striated 

 muscle are : 



Proteins. Myosinogen and Paramyosinogen. 



Pigment. Myohaematin. 



Fat. 



Nitrogenous extractives. Creatine. 



Hypoxanthine. 



Xanthine. 



Carnosine. 



