458 



EESPIKATION. 



large domestic quadrupeds, into a third, much smaller than 

 either of the other two. Each of these tubes or bronchi, 

 again, divides into secondary bronchial tubes, these again 

 into tertiary, and so on until they are reduced to about -^th 

 of an inch in diameter, when they individually terminate in 



Fig. 127. (WATERS.) Ultimate bronchial tubes, with air sacs connected with it 

 (of a cat), a, Ultimate bronchial tube, forming the point de reunion of all the air sacs; 

 c cc, the air sacs; d d, the alveoli; e e, opening leading to other sacs. At/, a part of 

 the wall separating two other air sacs is seen, the whole of which sacs could not be in- 

 cluded in the sketch. The drawing was made from the image reflected by the camera 

 lucida, 



a dilatation which opens into the ultimate air sacs and cells. 

 The bronchial tubes differ from the trachea in being nearly 

 circular, and having their cartilages disposed in plates in 

 place of rings. Three or four of these plates generally unite 



