DISEASES OF THE RESPIRATORY ORGANS. 
By W. H. Harsavesu, V. 8. 
[Revised by Leonard Pearson, B. 8., V. M. DJ 
The organs pertaining to the respiratory function may be enu- 
merated in natural order as follows: The nasal openings, or nostrils; 
the nasal chambers, through which the air passes in the head; the 
sinuses in the head, communicating with the nasal chambers; the 
pharnyx, common to the functions of breathing and swallowing; 
the larynx, at the top of the windpipe; the trachea, or windpipe; the 
bronchi (into which the windpipe divides), two tubes leading from 
the windpipe to the right and left lungs, respectively; the bronchial 
tubes, which penetrate and convey air to all parts of the lungs; the 
lungs. 
The pleura is a thin membrane that envelops the lung and lines the 
walls of the thoracic cavity. The diaphragm is a muscular structure, 
completely separating the contents of the thoracic cavity from those 
of the abdominal cavity. It is essentially a muscle of inspiration, 
and the principal one. Other muscles aid in the mechanism of res- 
piration, but the diseases or injuries of them have nothing to do with 
the diseases under consideration. a 
Just within the nasal openings the skin becomes wesdanily but per- 
ceptibly finer, until it is succeeded by the mucous membrane. Near 
the junction ee the skin and membrane is a small hole, presenting 
the appearance of having been made with a punch; this is the open- 
ing of the lachrymal duct, a canal that conveys the tears from the 
eyes. Within and above the nasal openings are the cavities, or fis- 
sures, called the false nostrils. The nasal chambers are completely 
separated, the right from the left, by a cartilaginous partition, the 
nasal septum. Each nasal chamber is divided into three continuous 
compartments by two thin, scroll-like turbinated bones. 
The mucous membrane lining the nasal chambers, and, in fact, the 
entire respiratory tract, is much more delicate and more frequently 
diseased that the mucous membrane of any other part of the body. 
The sinuses of the head are compartments which communicate with 
the nasal chambers and are lined with a continuation of the same 
membrane that lines the nasal chambers; their presence increases the 
volume and modifies the form of the head without increasing its 
weight. 
The horse, in a normal condition, breathes exclusively through the 
nostrils. The organs of respiration are quite liable to become dis- 
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