DISEASES OF THE RESPIRATORY ORGANS. 



By \V. II. llAKiJArcii. V. S. 

 [Rovis.d by T.couaril Pesirson, B. S., \. M. D.] 



The organs portiiiniiio: to the respiratory function may ])e enii- 

 mei'ated in natural older as foHows: The luisal openings. (»i- nostrils: 

 the nasal chamhers, through which the air passes in tlic head: the 

 sinuses in the head, coinnuinicatinfj with the nasal chauihei.s; the 

 l)harny.\, common to the functions of hreathin<; and swallow iufj;; 

 the hirynx, at the top of the windpipe: the trachea, or windpipe: the 

 bronchi (into which the windpijie divides), two tubes leadin*; from 

 the windpipe to the ri<;:ht and left lunijs. respectively: the bionchial 

 tubes, which penetrate and convey air to all parts of the hmgs: the 

 lunofs. 



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 ca^ ity. It is essentially a muscle of inspiration, 

 and the piincipal one. C)ther muscles aid in the mechanism of res- 

 pi lation. but the disea.ses or injuries of them have nothing to do with 

 the diseases under considei'ation. 



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

 ceptibly finei-, until it is succeeded l>y the mucous membrane. Near 

 the junction of the skin and membrane is a small hole, i)resenting 

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

 ing of the lachrymal duct, a canal that conveys the tears fiom the 

 eyes. A\'ithin and abo\e 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 ]>artition. the 

 nasal septum. Kach nasal chamber is divided into three continuous 

 compartments by two thin, scroll-like turbinated bones. 



The mucous membrane liniiiir the nasal chambei-s. and, in fact, the 

 entire respiratory tract, is much moie delicate and more fre<|uently 

 diseased that the mucous membrane of any other part of the body. 

 The sinuses of the head ai'e compartments which connnunicate with 

 the nasal chambei> and aie lined with a continuation (»f the same 

 membrane that lines the nasal chamlxM-s: their presence increases the 

 volume and modifies the form of the head without increasing its 

 weight. 



The horse, in a normal condition, breathes exclusively throiigli the 

 nostrils. Tlie organs of resj^iration are (piite liable to Wcome dis- 



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