In Case 4 are shown those ingredients of food, which are capable of forming muscle or flesh. They are made use of in the human body partly for the construction of muscle, and partly for the production of mechanical force and heat. They are all nearly identical in their chemical composition. 1. ALBUMEN, made from Eggs and from Blood. It forms about 7 parts in 100 of blood, and is always present in lymph and chyle. Liquid or soluble albumen, as shown in the white of egg, coagulates by heat and various chemical agents. 2. ALBUMEN, as found in the juices of carrots, turnips, and cabbages, and obtained by boiling their juices. It is the same body as albumen from eggs. 3. FIBRIN made by stirring blood with a rod. It is the basis of muscle or flesh. Flesh-fibrin probably bears the same relation to blood-fibrin as coagulated albumen does to soluble albumen. 4. FIBRIN made from Wheat-flour. It is identical with the fibrin found in flesh, but not exactly the same as that found in blood, and is known as _Gluten_. 5. CASEIN prepared from milk, in which it is soluble, owing probably to a little alkali: when an acid is added, the Casein curdles or coagulates, and then is known as Cheese. In 100 parts of cows’ milk there are 3½ parts of Casein. 6. CASEIN or LEGUMIN as found in peas, beans, lentils, coffee, &c. The Casein of Vegetables is now supposed by most chemists to be identical with the Casein or Cheese of Milk, but a few chemists still deny this. 100 parts of peas contain above 20 parts of Casein. EGGS. Eggs are very nutritious articles of food. They contain as much oil or fat and flesh and force-producing matter as butcher’s meat. The white is not, however, so digestible as the flesh of meat. They enter into the composition of puddings, cakes, buns, and other forms of diet. They are also eaten alone, boiled or fried, and are most digestible when least done. The egg of the domestic fowl is usually eaten, but those of other birds are frequently employed as food. The eggs of the woodcock, plover, and other small birds, are esteemed a luxury. Those of the duck and goose have a strong flavour, and those of sea-fowl are fishy. The eggs of the turkey are rich in flavour, whilst those of the guinea-hen have a very delicate flavour. All birds’ eggs may be eaten with impunity. The eggs of the crocodile, and other oviparous reptiles, are eaten in some parts of the world. In Case 61 is a collection of the Eggs of domestic poultry and some other birds, together with the analysis of Hen’s Eggs. * * * * *