FIFTEENTH LECTURE. 



THE LUNGS. 



THE lungs originate in the same manner as the racemose 

 glands, but acquire an essentially different texture. Their 

 efferent canal system requires an especial preliminary dis- 

 cussion, on account of its peculiarity and complication. 



The cartilages of the larynx are hyaline, as the thyroid and 

 cricoid cartilages. In certain parts of the arytenoid cartilages 

 there is an elastic metamorphosis. The Wrisbergian and 

 Santorinian cartilages, with the epiglottis, are pure reticular 

 cartilage. The triticeaen cartilages are formed of hyaline or 

 connective-tissue cartilaginous substance. The ligaments of 

 the larynx present a considerable wealth of elastic tissue. 

 The lower true vocal cords are purely elastic. The muscles 

 are transversely striated. The mucous membrane, rather 

 compact and likewise not poor in elastic elements, shows 

 embedments of lymphoid cells. It contains racemose, true 

 mucous glands. 



Strongly stratified pavement epithelium covers the anterior 

 surface of the epiglottis ; there are not so many layers in that 

 covering the posterior surface as far as the base ; the same is 

 also true of the lower vocal cords. Otherwise, we meet with 

 slightly stratified ciliated epithelium, which descends far down 

 into the lungs. 



The wind-pipe or trachea, with its system of branches, the 

 bronchi, presents a fibrous tube, in the anterior wall of which 

 are embedded half rings of hyaline cartilage (annuli carti- 

 laginei). A deeper layer of transverse smooth muscles con- 

 nects the terminal portions of the half rings posteriorly. In 

 the mucous membrane we again meet with numerous mucous 

 glandules. 



