106 



eitlier in tlie class called "roarers," or are affected with "lieaves," 

 and therefore no separate classification is needed. Mares heavy with 

 foal, horses excessively fat, and those that have not been exercised 

 for so long that the muscular system has become unfit for work ; horses 

 with large bellies, and, especially, when the stomach is loaded with 

 coarse, fibrous, or bulky food, emit a louder sound than natural in 

 their breathing, and are called "thick-winded." The treatment in 

 such cases is obvious: "Remove the cause and the effect will cease." 

 AVhile it must be admitted that "thickening of the mucous mem- 

 brane of the finer bronchial tubes and air cells may cause the breath- 

 ing called "thick- winded," it must at the same time be admitted that 

 there is no symptom by which the condition can be distinguished 

 from what will hereafter be described as "heaves," by the general 

 reader, at least. 



THE WINDPIPE. 



The windpipe, or trachea, as it is technically called, is the flexible 

 tube that extends from the larynx, which it succeeds at the throat, 

 to above the base of the heart in the chest, where it terminates by 

 dividing into the right and left bronchi, the tubes going to the right 

 and left lung respectively. The windpipe is composed of about fifty 

 incomplete rings of cartilage united by ligaments. A muscular layer 

 is situated on the superior surface of the rings. Internally the tube is 

 lined with a continuation of the mucous membrane that lines the entire 

 respiratory tract, which here has ver}^ little sensibility in contrast 

 to that lining the larjnix, which is endowed with exc^uisite sensitiveness. 



The windpipe is not subject to any si^ecial disease, but is more or 

 less affected during laryngitis (sore throat), influenza, bronchitis, etc., 

 and requires no special treatment. The membrane may be left in a 

 thickened condition after these attacks. One or more of the rings 

 may be accidentallj^ fractured, or the tube maj^ be distorted or mal- 

 formed, the result of violent injury. After the operation of trache- 

 otomj'" it is not uncommon to find a tumor or malformation as a result 

 or sequel of the operation. In i^assing over this section attention is 

 merely called to those defects, as they require no particular attention 

 in the way of treatment. However, it may be stated that any one of 

 the before-mentioned conditions may constitute one of the causes of 

 noisy respiration described as "roai'ing." 



GUTTURAL POUCHES. 



These two sacs are not included in the organs of respiration, but 

 sometimes pus collects in them to an extent that considerably inter- 

 feres AA'ith resi^iration. They are in close x^roximity to the pharynx 

 and larynx, and when filled with matter the functions of the last- 

 named organs can not be prox)erly performed. They are situated 

 above the throat, and communicate with the jiharynx, as well as with 



