58 



ring of cartilage, studying carefully the structure of each coat. 

 Compare the lining epithelium with that in the ventricle of the 

 larynx and upon the soft palate. Note especially the overlapping 

 of the ends of the cartilaginous rings and the character of the epi- 

 thelium in the fold of the mucosa caused thereby, and the relation 

 of the muscle to the cartilage. In the last respect, compare with 

 the relations in man and sheep, as demonstrated to you. 



123. Trachea. Cat (old). Transection. Picric alcohol; 

 collodion ; sections fx. Stain with hematoxylin and picro- 

 fuchsin. 



Recognize in this preparation exactly the same structures ident- 

 ified in 122 and compare the two preparations, especially as to the 

 epithelium lining the fold where the cartilages overlap. This will 

 illustrate how the original character of an epithelium is altered by 

 changed conditions. 



LUNG. 



124. Lung. Transection (or lorigisection) of a lobe 

 (in part). Picric alcohol ; collodion ; sections //. Stained in 

 to to. 



Examine the gross preparations of lung, showing the lobes, 

 and the appearance of lung tissue seen in surface view and in sec- 

 tion. Is a further division of lobes into lobules recognizable ? The 

 section will illustrate the structure of normal lung. 



The following features are to be noted : (a) the general struc- 

 tural appearance of lung tissue, (i) the structure of a bronchus or 

 bronchiole, (c) the infundibula with air sacs opening into them, and 

 (of), if possible, the transition of terminal bronchus or alveolar duct 

 to infundibulum. 



125. Dried lung. Cat. The fresh lung was inflated and 

 dried. Prepare a slide with a rubber cell (§ 103, 6), and mount 

 within the cell two sections of lung cut free-hand, a surface section 

 and a deep section, mounting the surface section pleural side up. 

 Cover and seal (§ 103, 6). 



This preparation will illustrate well the infundibula and the 

 compartments in their walls, the air sacs. It is possible that there 

 may be a good natural injection of the blood capillaries (filled with 

 blood, — yellow) ; if so, note the size of the capillaries and the dense- 

 ness of the net-work. 



