Ixxxii 



rings : c, prominence on the back of the trachea : rf, section of 

 the cutaneous covering ; e, of the muscular ; f, the lining 

 mucous 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, b, c, as in last figure. 

 Figi 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 ; d d, mucous membrane of the trachea 

 and sac. 



