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.