CH. 



EPITHELIUM. 



epiblast or hypoblast. Hence it has received a distinct name, 

 viz. : endothelium. 



The general appearance presented by endothelium in serous 

 membranes is shown in figs. 29, 30, and 31 ; in blood-vessels in 



fig- 32- 



The stomata seen in some of the drawings are minute openings 

 surrounded by more darkly staining cells, which lead from serous 

 cavities into lymphatic vessels. 



Cubical, Spheroidal, and Columnar Epithelium. 



In these forms of epithelium, the cells are not flat, but are 

 thick ; if they approximate cubes or spheres in shape, the epi- 

 thelium is called cubical or spheroidal respectively. Spheroidal 

 epithelium is found in the alveoli of secreting glands, such as the 

 salivary glands, liver, and pancreas (see figs. 33 and 34), and will 



- 33- Glandular epithelium. Small lobule of a 

 mucous gland of the tongue, showing nucleated 

 glandular cells, x 200. (V. D. Harris.) 



Fig. 34. A small piece of the liver 

 of the horse. (Cadiat.) 



be discussed at length in connection with those organs. Cubical 

 epithelium is found in the alveoli of the thyroid (see fig. 35), in 

 the tubules of the testis, and in the ducts of some glands. 



In columnar epithelium the cells are tall, and form a kind of 

 palisade or rows of columns. It is found lining the interior 

 of the stomach and intestines, and the ducts of the majority of 

 secreting glands ; it forms also the layer on the outer surface 

 of the ovary. 



In the intestinal epithelium each cell has a distinct brightly 

 refracting and striated border. Fig. 36 shows two isolated cells 

 of this kind. 



