59 



126. Lung. . Injected with Berlin blue gelatin 

 mass (§ 128) ; alcohols ; collodion ; sections /i. No staining. 



Search the preparation to find places showing well the capillary 

 net-work in the walls of the air sacs, and compare it with the natural 

 injection, if present, in 125. 



127. Respiratory epithelium. Cat. Demonstration. Free- 

 hand section of silvered lung. The blackened cell cement outlines 

 the cells lining the air sacs, of which recognize the two kinds, large 

 flat cells with irregular outlines and small granular cells. Understand 

 the significance of the two kinds. 



THYROID. 



128. Thyroid. Chrome-oxalic ; parafi&n ; sections 

 jA.. Stain with hematoxylin and eosin. Consult the gross 



preparations for the position, shape (general), and color of the 

 glands ; their appearance superficially and in section. In the sec- 

 tion there are to be noted, the shape, size, and structure of the 

 acini ; the colloid mass ; the connective tissue dividing the gland 

 into lobes and lobules ; the blood vessels. Study well the epitheli- 

 um in connection with the formation of the colloid mass. Can you 

 recognize two kinds of cells ? This is a ductless gland ; in what 

 way may the secretion be utilized by the body ? 



