ristics,
however.

~Albumins.~--The best examples are found in egg albumin (white of
egg), lactalbumin (milk), serum albumin (blood), leucosin (wheat),
legumelin (peas). Albumins are all soluble in pure water, and are
coagulable by heat. Coagulation, due to the action of the ferments in
the body, takes place in milk, blood, and muscle plasma. Certain
albumens are particularly adapted for the building and repairing of
tissues. Among those that have been used in feeding experiments to
determine whether or not they were capable, when used as the sole
protein in the diet, of maintaining animals in normal nutrition, and
of supporting normal growth in the young animal,--may be cited
lactalbumin and egg albumin. These experiments provided diets adequate
in other respects, the object being to determine the value of the
various proteins. It was found that the albumin from milk was more
efficient in this respect than the egg albumin.[5]

In the invalid dietary the solubility of the albumins in water makes
them of especial value as reinforcing agents, since they may be
introduced into fluids without materially altering either their flavor
or their bulk.

~Globulins.~--Simple proteins, insoluble in pure water, but soluble
in neutral salt solutions; examples, muscle globulin, serum globulin
(blood), edestin (wheat), physelin (beans), legumin (beans and peas),
tuberin (potatoes), amandin (almonds), arachin, and conarachin
(peanuts).

~Alcohol-Soluble Proteins.~--Simple proteins soluble in alcohol of
from 70-80% strength. Insoluble in absolute alcohol, water and other
neutral solvents. Examples of these proteins may be seen in the
gliadin of wheat, zein of corn, and hordein of barley.

~Albuminoids.~--These substances represent one group of incomplete
proteins, inasmuch as they cannot alone support protein metabolism.
However, they are classed with the proteins and may be substituted for
at least a part of these compounds in the daily dietary, since they
are able to do much of the work of the pure proteins. The best example
of this group is seen in gelatin. This substance contains many of the
structural units of meat protein but in very different relative
amounts. It has not, therefore, the chemical units necessary to repair
the worn-out parts of cell machinery.[6]

~Conjugated Proteins:--Nucleoproteins, Phosphoproteins and
Hemoglobin.~

(a) ~Nucleoproteins.~--This type of protein is characteristic of all
cell nuclei, and i