PROCESS OF DIGESTION AFTER RUMINATION.--Following rumination which,
strictly speaking, is the first step in the digesting process, the food
passes into the third stomach. The fine parts pass right along to the
fourth stomach while the coarser parts are drawn between the folds of
the membrane in this division and worked about until it is fine and
ready to pass into the fourth stomach, where it becomes fully digested
by the action of acids and gastric juices which are secreted in this
part. It then passes into the small bowels, and is acted upon by the
bile from the liver and the pancreatic juice from the pancreas. These
juices are emptied into the first part of the small bowels through
little ducts or tubes, which lead from the glands down to the bowels,
just on the same principle as that of the horse. After this, throughout
the rest of the bowels, the nourishment of the food is taken into the
system by means of little glands which are situated in the coating of
the bowels. The nourishment when once in the blood goes to supply the
different parts of the body, while the part containing no nourishment
or undigested passes off through the back bowels in the form of feces.
TEETH.
Teeth are objects situated in the upper and lower jaws. They are made
of the same tissues as bone but contain 10-1/2 per cent. more of earthy
salts. This fact accounts for their extreme hardness. Unlike bone they
can stand exposure to air and friction without becoming diseased. Teeth
are used to masticate or chew the food, and because of the constant
change in their formation and appearance they serve as a guide in
telling the age of the horse.
There are three hard structures that enter into the formation of the
teeth--Dentine or Ivory, Enamel, and Cementum, or Crusta Petrosa.
The Dentine, or ivory, is situated in the upper part around the pulp or
nerve cavity. It is of yellowish color and largely supplied with nerves
which pass through it from the pulp cavity.
The Enamel is the hardest substance of the tooth, and covers the
outside of all the exposed part. This substance is characterized by its
whiteness and, unlike the dentine, contains no blood vessels or nerves.
If part of the enamel is broken off it is never replaced, and the tooth
below the broken part generally becomes decayed.
The Cementum, or crusta petrosa, is found in the fang or root and the
parts situated below the gum. It is the softest part of the tooth.
Teeth may be simple or compound. Simple as in the dog, where the entire
exposed surface is covered by a solid cap of enamel, which alone is in
wear; compound or complex, as in the horse, where various tissues are
in wear. A tooth consists of the following anatomical parts: The body,
or crown, that part above the gum; the table, the part that comes into
wear on the top; the neck, the part to which the gums are attached; and
the fangs or roots, the parts situated down in the bone.
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