46 THE LARYNX AND TRACHEA, BY E. VERSON. 



recurrent laryngeal nerves, previously to their ramification in 

 the substance of the muscles, appear to be mingled with nu- 

 merous ganglion cells. According to Luschka, the real termina- 

 tion of the nerves is effected by means of pyriform or oval 

 corpuscles, having a diameter of O0035 of a millimeter, to each 

 of which a fine axis-cylinder runs, that usually terminates in a 

 slight enlargement, 



B. TRACHEA. 



The framework of the trachea is composed of from fifteen to 

 twenty incomplete cartilaginous rings, which, being open behind, 

 resemble a horseshoe in form. Variations of this form occur 

 especially at the upper and lower extremities of the trachea, 

 where the rings frequently divide, and join with the ring above 

 or below; the enumeration of the individual rings is thus 

 rendered very difficult. 



Small masses of cartilage may occasionally be found scattered 

 between the free extremities of the rings, and, like them, con- 

 sist of hyaline cartilage. Similar masses occur sometimes in 

 animals. 



In the Dog, Cat, Sheep, etc., the cartilaginous rings represent, as in 

 Man, segments of circles. In the quiescent condition they are almost 

 in contact, whilst on contraction of the muscular layer they overlap 

 each other, causing the mucous membrane to project into the lumen 

 of the trachea in the form of longitudinal folds, having a breadth of 

 from 3 to 4 lines. 



Running from the lower border of the cricoid cartilage to the 

 first ring of the trachea, as well as between the several rings 

 throughout the whole length of the tube, are highly elastic 

 bands, mingled with connective tissue, which bind the whole 

 framework together. Numerous bands of a similar nature 

 radiate also from the lower border of each ring into the sub- 

 mucous tissue. 



The inner surface of the trachea is lined by a mucous mem- 

 brane, having a thickness of - 13 to 0'15 of a millimeter, 

 characterized by the remarkable abundance of longitudinal 

 plexuses of elastic tissue. This membrane is sometimes bounded 

 internally by a thin hyaline layer, which has been regarded as 



