4GO 



THE EESPIRATOEY APPARATUS IN MAMMALIA. 



of the brachial arteries supply it with blood. Its nerves come from the 

 recurrent s they show small ganglia on their track. 



Functions. Except as a tube for the passage of the inspired and expired 

 air, the trachea performs no other function. 



3. The Bronchi. (Fig. 232.) 



Preparation. After removing the lung from the thoracic cavity, it is filled with water 

 by fixing the trachea to a water-tap. The bronchi may then be dissected by tearing 

 and triturating the pulmonary tissue. 



Each of the two bronchi the terminal branches of the trachea resembles 

 a tree imbedded in the substance of the lung, and sending out a multitude 

 of branches. 



Fig. 232. 





BRONCHIAL TUBE, with its Bronchules and Ultimate Ramifications (natural size). 



Disposition. At a short distance from their origin, the bronchi enter 

 the lobes of the lung, and pass backwards and outwards towards the 

 superior part of the base of the organ, giving off in their course large 

 collateral branches until they themselves are expended. These branches 

 originate alternately above, within, below, and outwards ; and thus extend 

 in every direction. The first forms an obtuse angle with the principal 

 trunk, and is directed forwards, to ramify in the anterior lobule of the 

 lung ; the others are detached at an angle more or less acute. All are 

 subdivided into gradually-decreasing branches, which soon become of a 

 capillary diameter, and finally open into the pulmonary air-cells. (See 

 STRUCTURE OF THE LUNGS.) 



