144 THE BRONCHIAL TUBES. 



above and below, about half the width of each ring, should be 

 excised with the intervening ligament. The remaining portion 

 will then be strong enough to retain the perfect arched ibrm of 

 the trachea. 



If the orifice is only to be kept open while some foreign body 

 is extracted, or tumor removed, or ulcer healed, or inflammation 

 subdued, nothing more is necessary than to keep the lips of the 

 wound a little apart, by passing some thread through each, and 

 slightly everting them, and tying the threads to the mane. 



If, however, there is any permanent obstruction, a tube will 

 De necessary. It should be two or three inches long, curved at 

 the top, and the external orifice turning downwards with a little 

 ring on each side, by which, through the means of strings, it 

 may be retained in its situation. 



The purpose of the operation being answered, the flaps of in- 

 tegument must be brought over the wc-unds, the edges, if neces- 

 sary, diminished, and the parts kept in apposition by a few 

 stitches. The cartilage will be perfectly reproduced, only the 

 rings will be a Httle thicker and wider. 



THE BROI^CHIAL TUBES. 



After the windpipe has entered the chest, and continued 

 through the mediastinum to the base of the heart, it divides 

 into two tubes — the Bronchial tubes — which enter each lung, 

 where they are again subdivided into smaller tubes carrying air 

 to every portion and cell of the lungs. Before considering their 

 diseases, we will pause and consider the structure and functions 

 of the chest. 



