THE MICROSCOPE IN ANIMAL HISTOLOGY. 191 



terior layer of the cornea ; the peritoneal surface ; the 

 interior of bloodvessels, and shut sacs generally. 



2. Squamous or scaly epithelium. The cells are flat, 

 and overlap each other at the edges (Plate XVIII, 6, Fig. 

 142). 



Examples : Epidermis ; many parts of mucous mem- 

 branes, as the mouth, fundus of bladder, vagina, etc. 



3. Glandular epithelium (Plate XVIII, c, Fig. 142). 

 The cells are round or oval bioplasts, often polyhedral 

 from pressure, and the formed material is often soft. 



Examples : Liver cells, convoluted tubes of kidney, and 

 interior of glands generally. 



4. Columnar epithelium (Plate XVIII, d, Fig. 142). 

 Cells cylindrical or oblong, arranged side by side. A 

 bird's-eye view shows them similar to the tessellated form, 

 hence they should be seen from the side. 



Examples : Villi and follicles of intestine, ducts of 

 glands, urethra, etc. 



Some of the columnar or cylinder-cells have a thickened 

 border or lid perforated with minute pores (Plate XVIII, 

 /, Fig. 142). They are found in the small intestine, gall- 

 bladder, and biliary ducts. 



5. Ciliated epithelium (Plate XVIII, e, Fig. 142). 

 These are cylindrical cells having vibratile cilia, whose 

 motions produce a current in the surrounding fluid. 



Examples: The upper and back nasal passages, the 

 pharynx; bronchi, Fallopian tubes, etc. 



The Hair. Hairs are filiform appendages, composed of 

 a modified epithelial tissue of rather complex structure. 

 They originate in a follicle, which is a folding in of the 

 skin. The shaft of the hair is the portion projecting 

 above the skin, and the root is concealed in the hair-fol- 

 licle. The bulb of the root is the rounded terminal part, 

 which is hollow below, and rests on a papilla which rises 

 from the floor of the follicle (Plate XIX, Fig. 143). Be- 

 tween the follicle and hair is a sheath, which is divided 



