EPITHELIUM. 



43 



stratified pavement-epithelium has been termed prickle cells. These cells possess 

 short fine fibrils which pass from their margins to those of neighboring cells, serv- 

 ing to connect them together. They were first probably noticed by Max Schultze 

 and Yirchow, and it was believed that by them the cells were dovetailed together. 

 Subsequently this was shown not to be so by Bizzozero, who pointed out that the 

 prickles were attached to each other by their apices and formed minute bridges 

 across spaces occurring between the cells of the epithelium. 



The columnar or cylindrical epithelium (Fig. 8) is formed of cylindrical or 

 rod-shaped cells, each containing a nucleus, and set together so as to form a com- 



FIG. 8. Epithelium of the intestinal villi 

 of the rabbit. Magnified 300 times, a. Base- 

 ment-membrane. 



FIG. 9. Simple columnar epithelium, from the mucous 

 membrane of the intestine, with goblet-cells pouring out 

 their contents. (Klein and Xoble Smith.) 



plete membrane. The cells have a prismatic figure, more or less flattened from 

 mutual pressure, and are set upright on the surface on which they are supported. 

 Their protoplasm is always more or less longitudinally striated, and they contain 

 a nucleus which is oval in shape and contains an intranuclear network. 



This form of epithelium covers the mucous membrane of nearly the whole 

 gastro-intestinal tract and the glands of that part, the greater part of the urethra, 

 the vas deferens. the prostate. Cowper's glands, Bartholini's glands, and a portion 

 of the uterine mucous membrane. 



/ G-oblet- or chalice-celis are a modification of the columnar cell. They appear 

 to be formed by an alteration in shape of the columnar epithelium (ciliated or 

 otherwise) consequent on the secretion into the interior of the cell of mucin, the 

 chief organic constituent of mucus, which distends the upper part of the cell, 

 while the nucleus is pressed down toward its deep part, until the cell bursts and 

 the mucus is discharged on to the surface of the mucous membrane, as shown in 

 Fig. 9. 



The spheroidal or glandular epithelium (Fig. 10) is composed of circular or 

 polyhedral cells. Like other forms of epithelial cells, the protoplasm is a fine 



FIG. 10. Spheroidal epithelium. Magnified 

 250 times. 



Fu;. 11. Ciliated epithelium from the human 

 trachea. Magnified 350 times, a. Innermost layers 

 of the elastic longitudinal fibres. 6. Homogeneous 

 innermost layers of the mucous membrane, c. 

 Deepest round cells, d. Middle elongated cells, e. 

 Superficial cells, bearing cilia. . 



reticulum. which gives to the cell the appearance of granulation. They are found 

 in the terminal recesses of secreting glands, and the protoplasm of the cells 

 usually contains the materials which the cells secrete. 



Ciliated epithelium (Fig. 11) may be of any of the preceding forms, but usually 



