44 THE TISSUES. 



gradually flattened toward the surface, and are germinal cells 

 which ultimately become squamous. This variety is of exten- 

 sive distribution, forming the epidermis of the skin and the 

 epithelial layer of the conjunctiva, mouth, part of the pharynx 

 and larynx, oesophagus, vagina, and portions of the urethra. 



The 'epithelium lining the bladder, ureters, and pelvis of 

 the kidneys is a variety of stratified squamous epithelium 

 sometimes called transitional epithelium (Fig. 12). The num- 

 ber of layers of cells is few, forming a sort of intermediate 



FJG. 12. 



Transitional epithelium, bladder of mouse (Dogiel). 



or transitional variety between the simple and stratified types. 

 The lower cells become quickly changed into the flattened 

 surface cells. 



Columnar epithelium non-ciliated: Columnar epithelium- 

 cells are elongated, columnar, or prismatic in shape, arranged 

 on a basement-membrane perpendicular to it, with one end di- 

 rected outward. Sometimes they are shorter and more 

 cuboidal. 



When they form a single layer they constitute simple col- 

 umnar epithelium (Fig. 13), which occurs throughout the 

 stomach and intestine, in some gland-ducts, covering the ovary, 

 and in portions of the male urethra and seminal tracts. 



Non-ciliated stratified columnar epithelium, in which the cells 



