285 
self: (see Fig. 1 and 2, Plate 4) this part 
consists of the same cartilaginous rings as the 
rest of the windpipe, and in fact is only a 
great enlargement of the same structure, 
being at least four times the diameter of 
any other part; this is the appearance the 
trachea assumes when the air is drawn into 
the lungs ; but when the air is propelled 
from the lungs, this part is so formed by 
the inequality of its cartilaginous annula- 
tions, and intermediate membranes, that it 
contracts itself to little more than one third 
of its length, and is at the same time consi- 
derably compressed, (see Fig. 6, Plate 3). 
