SUBSTANCES FORMING THE BODY; OXIDATION 53 



the tissues firmness and strength such as sugar and fats 

 containing no nitrogen cannot give. Albumin is a very 

 complex substance which only plants can form. Animals 

 must get it from vegetables, for it is the essential part of all 

 living cells. It is similar to the white or albumen of an egg. 

 Because it turns white when heated, it is called albumen 

 (Latin albus, white). Pure albumin is hard and brittle, as 

 the white of an egg is when dried. The albumin of the body 

 is a solution in from five to twenty-five times its own 

 weight of water. In the blood it is liquid, in the flesh 

 it is jellylike, in the connective tissue of the skin it is tough 

 and strong. Albumin may be hardened or coagulated by 

 heat ; the albumen of a boiled egg is an example. Coagu- 

 lation of its albumin destroys the life of a cell. Lean meat, 

 cheese, animal gelatine, glue, and gluten are forms of albu- 

 min. About four and one half ounces of pure albumin 

 per day are necessary to supply the body in winter. 



87. Fats. Fats are smooth, greasy substances that be- 

 come liquid when heated ; those that are liquid at ordinary 

 temperature are called oils. Fat is always oil in the living 

 body and is stored in thin-walled cells in connective tissue 

 (Fig. 38). Fat is a simple substance compared to albu- 

 min ; divided in tiny particles or globules, and floating in 

 water, it forms an emulsion. Milk is an emulsion. No 

 emulsions are permanent ; e.g. the cream rises in the milk in 

 a few hours. Fat is a living garment to the body lying 

 underneath the skin to retain heat, protect from the cold, 

 and round out the form. It is a cushion for protection and 

 a store of heat-producing food to be used in sickness or at 

 any time when food cannot be eaten. About three ounces 

 of fat should be eaten each day in winter. 



88. Starch and Sugar (Carbohydrates). Starch is 

 abundant in young plants. As the plant grows the 

 starch is changed to wood. Fruit while green is chiefly 

 starch ; but as it ripens, the starch is changed to sugar. 



