These are by far the most characteristic organic compounds existing in the body; they are only known as obtained from living beings, having never yet been artificially constructed in the laboratory; a good example is found in the white of an egg, which consists chiefly of albumen dissolved in water. All the tissues of the body which have any marked physiological property contain some albuminous substance, only-such things as hairs, nails, and teeth being devoid of them. All albuminous bodies contain nitrogen, carbon, hydrogen, and oxygen; most of them sulphur and phosphorus in addition. The more important ones found in the body are, (1) Serum albumen, very like egg albumen, and found dissolved in the blood, along with another named (2) fibrinogen, which turns into (3) fibrin, when blood clots; (4) Myosin, found in the muscles and " setting" or coagulating after death, when it causes the death stiffening; (5) Casein, found in milk, and forming the main bulk of cheese.

Fats belong to the organic compounds in the body which contain no nitrogen; they consist solely of carbon, hydrogen, and oxygen. The chief fats in the body are palmatin, stearin, and olein; by proper treatment each can be split up into glycerine and a fatty acid; palmitic, stearic, or oleic acid as the case may be.

What is found in addition in some of them ? How many chief varieties of organic compounds are there in the body ? Name them.

Give another name for albuminous substances. Can they be made artificially? Give an example of an albumen. What elements do albumens contain ? Name the more important albumens of the body. Where are they found ?

What elements do fats contain ? Name the chief fats of the body. Into what may they be decomposed ?

The carbohydrates also consist entirely of carbon, hydrogen, and oxygen; they belong to the same class of substances as starch and sugar. The most important carbohydrate in the body is glycogen, a sort of starch found stored up in the liver and muscles. Glucose or grape sugar also exists in the body; and lactose or milk sugar is found in milk.

What elements do carbohydrates contain ? Name the most important found in the body ? Where is glycogen found ? Where milk sugar ?