DISEASES OF THE RESPIRATORY ORGANS. 



By ^V. IT. HARnAUGiT, V. S. 

 [Revised in 1903 by Leonard Pearson, B. S., V. M. D.] 



The organs pertaining to the respirator}' function ma}' be eniimeriited 

 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 pharynx, 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 thora<;ic 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 respiration, 

 but the diseases or injuries of them have nothing to do with the 

 diseases under consideration. 



Just within the nasal openings the skin becomes gradually but per- 

 ceptibly finer, until it is succeeded by the mucous membrane. Near 

 the junction of the skin and membrane is a small hole, presenting the 

 appearance of having been made with a punch; this is the opening of 

 the lachrymal duct, a canal that conveys the tears from the eyes. 

 Within and above the nasal openings are the cavities, or fissures, 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 cx3ntinuous compartments by 

 the 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 than the mucous membrane of any other part of the body. 

 The sinuses of the head are compartments which commiuiicate 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 more liable to disease than 

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