146 ALIMENTATION 



tose by the following process : Lactose (C 12 H 22 O 11 + H 2 O = dextrose, 

 C 6 H 12 O 6 + galactose, C 6 H 12 O 6 ). It does not of itself undergo fermen- 

 tation, but when it has been inverted by the action of yeast, it slowly 

 ferments. 



Maltose. This carbohydrate is the product of the action of malt- 

 diastase on starch. It is strongly dextro-rotatory. Boiled with dilute 

 mineral acids or exposed to the action of inverting ferments, it assumes 

 water and is converted into dextrose. It undergoes this change in 

 digestion. It reduces the salts of copper and promptly undergoes 

 alcoholic fermentation when mixed with yeast. Its empirical formula 

 is C 12 H 22 O n . 



Starch. This carbohydrate is of vegetable origin. It is composed 

 of hard granules that are insoluble in cold water. Treated with boiling 

 water, the granules swell, press together and gelatinize on cooling. 

 Under the influence of the diastatic ferments, it is first converted into 

 soluble starch, then into dextrin, and finally into dextrose. The em- 

 pirical formula of soluble starch is (C 6 H 10 O 5 ) 20 (?). Starch gives an 

 intense blue reaction with iodine, even in very small quantity. This 

 color is discharged by heat but reappears on cooling: 



Glycogen. Glycogen, or animal starch, is found in the liver, mus- 

 cular tissue, leucocytes and the blood of the hepatic veins. In the 

 liver the products of digestion of the carbohydrates of food are stored 

 up in the form of glycogen. Treated with iodine, glycogen gives a 

 reddish reaction. It is dextro-rotatory. 



Cellulose, Inosite and Gums. The hard covering of starch-granules 

 is composed of cellulose. By boiling starch, these coverings are rup- 

 tured, the starch is set free and it may be acted on slightly by 

 the digestive secretions. It exists in vegetable food, but on account 

 of its difficult solubility it is not readily digested. Treated with dilute 

 mineral acids for a long time, like starch, it is converted into glucose. 



Inosite, or the sugar of muscular tissue, exists in muscle, the liver, 

 the kidney and in various other parts in small quantity. 



. The gums exist in food and in the blood in very small quantity. 

 They are unimportant in the processes of nutrition. 



The Fats. Fats exist in the body either in the form of adipose 

 tissue or in granules and in some instances in molecular union with 

 nitrogenous matters. They present three forms, or varieties : triolein, 

 liquid at a temperature of 23 Fahr. (-5 C.); tripalmitin, liquid at 115 

 Fahr. (45 C.); tristearin, liquid at 128 Fahr. (53.66 C.). Fats are 

 regarded by chemists as compounds of fatty acids with glycerin, and 

 on this account they are sometimes called glycerids. It is incorrect to 

 call them hydrocarbons, a name by which they were formerly known. 



