The citizen. (Frederick City, Md.) 1895-1923, 1900-06-22
low THE HORSE EATS.
)NE OF NATURES REMARKABLE
PROVISIONS FOR OLD AGE.

ways Keep sharp--Use of Saliva as
an Aid to Dieesticn-lmportance of
Chewing.
A horse with a full mouth" has
orty-two teeth, namely, six front
.eeth in each jaw, and one tush and
six back teeth on each side Of each
aw, writes an English veterinarian
n the London Live Stock Journal.
Each tooth is covered with a very
hard, white and comparatively thin
layer of enamel, which in the front
teeth forms a depression in the cut
Ing surface table of the tooth. Hence.
when a front tooth comes into wear,
its table has two irregularly-shaped
rings Of enamel with soft tooth-sub-
stance (dentine) between them.
In each back tooth the layer Of en-
nmel is doubled in on each side so as
to form on the table sharp and hard
ridges, which project above the soft
dentine. The tables of the back teeth
slope downward and outward, that
is to say, their inner edges are higher
than their outer edges. The action of
the back teeth is that of a mill, in
which the sharp surfaC es of the up
per and lower back. teeth on each
side of the mouth work laterally
against each other, and thus grind the
food which is brought between them
by the tongue and cheeks.
AS the lower jaw IS narrower than
the upper jaw, the horse can chew
with his back teeth only on one side
of his mouth at time, which he often
continues to do for even so long as
an hour, without changing to the
other side. A horse is unable to use
his front teeth and his back teeth
at the same time; for when he works
his jaws laterally the front teeth Of
the lower jaw become separated from
those Of the upper jaw.
Each tooth is lodged in a socket Of
its jaw bone, and becomes developed
from its dental pulp, which is pro-
vided with blood vessels, nerves and
secreting cells. Owing to the con-
tinued secretion of dentine, the teeth
are forced slowly out of their sockets,
which movement more or less makes
up for the wear entailed on the teeth
by mastication.
Our own teeth, on the contrary, re-
main stationary in their sockets after
they have attained their full size
The greater amount of wear under
is compensated for by the increasing
obliquity of the incisors with age.
AS the teeth wear down In time,
the layers of enamel of both the front
and back teeth gradually become thin
ner and weaker, until at last they
disappear altogether, or fail to full.
flll their purpose as cutting projec-
tions on the tables of the teeth.
Hence, mastication becomes less per-
feet with age, and as the animal grows
old, he becomes increasingly liable to
indigestion from the faulty action of
his teeth.
On an average, horse takes about
nine minutes to eat one pound of oats,
and about twelve minutes to consume
the same weight of hay.
While the food is being chewed, Il
becomes more or less mixed with
saliva, which flows into the mouth
from the salivary glands in response
to the stimulus caused by the pres
ence of the food. and which helps the
animal to swallow. In horses, the
chief source of saliva Is the parotid
glands, which are Of greater COM
parative size in them than in all other
animals except ruminants.
The saliva of the parotid glands
consists of about S9.2 per cent. of
water. Carpenter points out that the
size of the parotid glands in animals
is proportionate to the degree in
which the mastication of their food is
performed; and that these glands are
absent in birds, which swallow their
food whole.
Although dogs secrete saliva abun.
dantly, starch is not a component of
their natural food. AS the require
ments of the horses digestion de.
mands that he should thoroughly
chew his food, we ought to give it to
him in condition that will induce
him to eat slowly. Furthermore, the
amount of saliva secreted during mas
tication is more or less proportionate
to the dryness OF the fodder; for the
dryer it is the more saliva will the
horse require to enable him to swal-
low it,
Saliva, being of an alkaline nature.
aids the digestion of fat by forming
1t into an emulsion, in which the fat
is split up into minute particles.
Saliva contains the ferment pytalln,
which has the property of converting
starch into sugar, in which form it is
absorbed into the body. The action of
the pytaline Of the saliva on starch Is
of too brief duration to have much
effect; for 1t ceases soon after the ar
rival of the food in the stomach, on
account of the presence of acid In the
gastric juices. The digestive changes
which the food undergoes in the
mouth therefore appear to be more
mechanical than chemical.