ng. Well smoked bacon cut thin and properly cooked is a
digestible form of fatty food, especially for tubercular patients.
Smoking improves the digestibility of ham.

SALTING.

Salting is one of the oldest methods of preserving food. The addition
of a little saltpetre helps to preserve the color of the meat. Brine
is frequently used to temporarily preserve meat and other substances.
Corned beef is a popular form of salt preservation. All salted meats
require long, slow cooking. They should always be placed in cold water
and heated gradually in order to extract the salt. Salt meats are less
digestible and not quite so nutritious as fresh meats.

FREEZING.

Food may be kept in a frozen condition almost indefinitely, but will
decompose very quickly when thawed, hence the necessity for cooking
immediately. Frozen meat loses 10 per cent. of its nutritive value in
cooking.

REFRIGERATING.

This process does not involve actual freezing, but implies
preservation in chambers at a temperature maintained a few degrees
above freezing point. This method does not affect the flavor or
nutritive value of food so much as freezing.

SEALING.

Sealing is accomplished not only in the process of canning but by
covering with substances which are impermeable. Beef has been
preserved for considerable time by immersing in hot fat in which it
was allowed to remain after cooling.

CHEMICALS.

Chemicals are sometimes used in the preservation of food, but the
other methods are safer.

CHAPTER V.

Foods Containing Protein, or Nitrogenous Matter.

Animal foods contain nutritive matter in a concentrated form, and
being chemically similar to the composition of the body is doubtless
the reason why they assimilate more readily than vegetable foods,
although the latter are richer in mineral matter. The most valuable
animal foods in common use are meat, eggs, milk, fish, gelatin and
fats.

MEAT.

Meat is composed of muscular tissue, connective tissue or gristle,
fatty tissue, blood-vessels, nerves, bone, etc. The value of meat as
food is due chiefly to the nitrogenous compound it contains, the most
valuable being the albuminoids: the gelatinoid of meat is easily
changed into gelatin by the action of hot water. Gelatin when combined
with the albuminoids and extractives has considerable nutritive value.
Extractives are meat bases, or rather meat which has been dissolved by
water, such as soup stock and beef tea. The object in c