pending
upon the quantity of fluid that is present and the size of the tubes in
which the sound is produced. According to their character they are divided
into dry and moist. The friction sound is produced by the rubbing together
of roughened surfaces and is characteristic of pleurisy.

_Percussion._--Percussion is that mode of examination by which we elicit
sounds by striking or tapping over the part. It may be direct or indirect.
If the middle finger of the left hand is placed firmly on the chest and
smartly tapped or struck with the ends of the first three fingers of the
right hand, the sound will be noticed to be more resonant and clear than
when the same procedure is practiced on a solid part of the body. This is
because the lungs are not solid, but are always, in health, well expanded
with air. In certain pulmonary diseases, however, as in pneumonia, they
fill up and become solid, when percussion produces a dull sound, like that
on any other solid part of the animal. When fluid has collected in the
lower part of the chest cavity the sound will also be dull on percussion.
Where there is an excess of air in the chest cavity, as in emphysema or in
pneumothorax, the percussion sound becomes abnormally loud and clear. By
practice on healthy animals the character and boundaries of the sounds can
be so well determined that any variation from them will be readily
detected, and will sometimes disclose the presence of a diseased condition
when nothing else will.

Percussion is sometimes practiced with the aid of a special percussion
hammer and an object known as a pleximeter to strike upon. A percussion
hammer is made of rubber or has a rubber tip, so that when the pleximeter,
which is placed against the side of the animal, is struck the impact will
not be accompanied with a noise. A percussion hammer and pleximeter may be
purchased from any veterinary instrument maker.

CATARRH (COLD IN THE HEAD).

Nasal catarrh is an inflammation of the mucous membranes of the nostrils
and upper air passages. Simple catarrh is not a serious disease in itself,
but if neglected is liable to be complicated with laryngitis, bronchitis,
pneumonia, plurisy, or other serious and sometimes fatal diseases of the
respiratory organs. Catarrh is a common disease among cattle. It is often
caused by sudden exposure to wet and cold after they have been accustomed
to shelter. It may arise from inhalation of irritating gases. It is also
sometimes pro