hundred pounds. Several cases are
on record of persons weighing eight hundred pounds.

453. As already mentioned, the blood is the nutritive fluid of
animals. When this fluid is coagulated, a thick, jelly-like mass
floats in the serum, called coagulum. This coagulated mass is composed
of fibrin, and red globulated matter. The color of the red globules is
owing to the presence of iron, though some physiologists think it
depends on an animal substance of a gelatinous character.

_Observation._ That portion of the serum which remains fluid after
coagulation by heat has taken place, is called _se-ros'i-ty_. It is
more abundant in the blood of old, than in that of young animals; and
it forms the "red gravy" in roasted meats.

454. The blood is not necessarily red. It may be white, as in most
fish. There is no animal in which the blood is equally red in all
parts of the body. The ligaments, tendons, and other white tissues in
man are supplied but sparingly with red blood. The fluid that supplies
these tissues is whitish.

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452. Of excessive nutrition in early life. 453. Describe the parts
that enter into the composition of the blood. What part of the blood
forms the red gravy in roasted meats? 454. Is the blood necessarily
red? Of what color is the blood of the fish? What part of the human
system has white blood?

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HYGIENE OF NUTRITION.

455. _Healthy nutrition requires pure blood._ If the nutrient arteries
of the bones are supplied with impure blood, they will become soft or
brittle, their vitality will be impaired, and disease will be the
ultimate result. The five hundred muscles receive another portion of
the blood. These organs are attached to, and act upon the bones. Upon
the health and contractile energy of the muscles depends the ability
to labor. Give these organs of motion impure blood, which is an
unhealthy stimulus, and they will become enfeebled, the step will lose
its elasticity, the movement of the arm will be inefficient, and every
muscle will be incapacitated to perform its usual amount of labor.

456. When the stomach, liver, and other organs subservient to the
digestion of food, are supplied with impure blood, the digestive
process is impaired, causing faintness and loss of appetite, also a
deranged state of the intestines, and, in general, all the symptoms of
dyspepsia.

457. The delicate structure of the lungs, in which the blood is or