~Adipose Tissue~ of man and animals, tallow of mutton, suet, and oleo
oil of beef, lard of pork.

~Phosphorized Fats~, which include lecithin and lecithans, occur
abundantly in the brain and nerve tissues and to a less extent in the
cells and tissues of man, animals, and plants of which it seems an
essential part. Egg yolk is the most abundant source of phosphorized
fat in food material, but milk likewise furnishes an appreciable
amount.

~Cholesterol~ (fat-like substances).--"The fatty secretions of the
sebaceous glands of man and of the higher animals which furnish the
natural oil for hair, wool and feathers," (Starling), lanoline, which
is a purified wool fat, consist chiefly of cholesterol. According to
Mathews, cholesterol is an essential constituent of the blood, and is
found in the brain and in nearly all living tissues. It is likewise
believed to be the "mother substance" from which bile acids are
derived.

~Fat Soluble "A."~--The vitamine factor which occurs dissolved in
certain fats, namely, milk (whole), butter, egg yolk, the organs of
animals, and codfish liver.

~Definition of Fat.~--The fats are all glycerides; that is, they are
substances made up of combinations of fatty acids and glycerine, which
constitute a definite group of chemical compounds, certain members of
which are liquid in form, while others are solid, or semi-solid. The
liquid fats are known as fatty oils. The fatty acids in which we are
chiefly concerned in this study are: Butyric, Stearic, Oleic, and
Palmitic. Most of the common fats owe their form and flavor to the
type and amount of the various fatty acids of which they are
composed. For example, butter is made up of ten fatty acids; but its
soft, solid form is due to the olein and palmitin (glycerides of oleic
and palmitic acids) which it contains; and its characteristic flavor,
as well as its name, to its butyric acid content (about 5 to 6%). It
is evident that the degree of softness or hardness of a fat may be
determined chiefly by the amount of oleic acid in its composition.
Most of the common oils with which we are familiar in food are
composed chiefly of olein. Stearin (the glyceride of stearic acid) is
the hardest of the fatty acids, while palmitin, although classed with
the solid fats, is not so hard as stearin. Lard and butter are higher
in olein and palmitin and are consequently semi-solid, while suet and
tallow, consisting chiefly of stearin, are much harder than the othe