1xxxil 
rings : c, prominence on the back of the trachea: d, section of 
the cutaneous covering; e, of the muscular; f, the lining 
muvous membrane, extending over the front and outside of the 
rings, and then continued round the edges of the opening 
into the trachea. 
Fig. 4.—Section of the trachea: a, 6, c, as in last figure. 
Fig: 5.—Posterior view of the sac: a, indentation on the 
trachea corresponding to the internal ridge in figs. 3 and 4; 
b, longitudinal elastic ligament, dissected off, and drawn to 
one side; c, transverse muscular fasciculi, attached to the con- 
vexities of the cartilages on either side, raised on a small twig. 
Fig. 6.—Horizontal view of three tracheal cartilages: a, 
from the upper portion; c, from the lower; b, corresponds to 
the opening, shews two semicircular cartilages, their posterior 
cornua projecting forwards into the tube, and ending in round 
and slightly bifid points; dd, mucous membrane of the trachea 
-and sac. 
