EPISTYLIS. 



[ 240 ] 



EPITHELIUM. 



Probably the young state of Dinobryon 

 sertularia, like which it contains a disk- 

 shaped nucleus. 



BIBL. Ehrenb. In/us, p. 123; Stein, 

 In/us, p. 205. 



EPISTYLIS, Ehr. A genus of Infusoria, 

 of the family Vorticellina. 



Char. Pedicle rigid (not contractile), sim- 

 ple or branched; all the bodies of the ani- 

 mals of the same form. Aquatic;= Vorticella 

 or Carchesium with a rigid pedicle. 



Stein has pointed out the occurrence of 

 the encysting process in the species of this 

 genus. The same author also indicates the 

 presence of a lid-like discoidal process, pro- 

 trusihle from the orifice, and, like the latter, 

 furnished with vibratile cilia ; but this does 

 not occur in all the species admitted by 

 Ehrenberg. The species are numerous, and 

 mostly attached to aquatic animals or 



E. anastatica (PI. 23. fig. 51 a, c). Body 

 small, conical, not plicate, anterior margin 

 large and projecting; pedicle dichotomous, 

 smooth, or covered with minute foreign bo- 

 dies; entire length 1-144 to 1-14"; of single 

 body, 1-288". 



E. grandis (PI. 23. fig. 51 b, single body). 

 Body large, broadly campanulate; pedicle 

 decumbent, slender, smooth, laxly branched, 

 not jointed, forming large tufts ; length of 

 body 1-140 to 1-120". 



E. vegetans (AnthopTiysa Mulleri, Duj.) 



BIBL. Ehrenb. In/us, p. 279 ; Stein, In- 

 fus. passim. 



EPITEA, Fr. See UREDINEI, PHRAG- 

 MIDIUM, and MELAMPSORA. 



EPITHELIUM. The membranous layer 

 lining the various internal cavities, and co- 

 vering the internal free surfaces of animal 

 bodies, as the mucous canals and cavities, 

 and their involutions forming the glands and 

 ducts, the serous cavities, the vessels, &c. 



It serves to form a protection to the sur- 

 faces, to secrete a lubricating liquid, by 

 which the effects of friction of one against 

 the other are prevented, and to separate 

 from the blood the special secretions of the 

 various glandular organs. 



It consists of one or more layers of nu- 

 cleated cells, the form and arrangement of 

 which are very variable. They are either 

 round, polygonal, spindle-shaped, cylindrical 

 or conical. 



Three kinds of epithelium are usually dis- 

 tinguished, but intermediate forms are also 

 met with. 



1. Pavement-, or tesselated, epithelium. 



This consists of one or more layers of 

 roundish, oval, or polygonal, flattened 

 cells, about 1-2000 to 1-500" in diameter, 

 and containing nuclei with nucleoli. It 

 occurs upon the surface of the serous and 

 synovial membranes ; the membrane of the 

 aqueous humour, the choroid, the capsule 

 of the lens, the retina, and the conjunctiva 

 of the bulb of the eye ; the cavity of the 

 tympanum ; the lower half of the pharynx, 

 the oesophagus, the endocardium; some 

 veins ; many glands and ducts, as the race- 

 mose, the sudoriparous and ceruminous 

 glands; the hepatic ducts; the vagina and 

 female urethra ; the bladder, uterus, pelvis, 

 and tubules of the kidneys ; and the lungs. 

 In the arteries and many veins the cells are 

 spindle-shaped. 



2. Cylindrical epithelium. In this form, 

 the cells are either cylindrical, conical, or 

 pyramidal, about 1-1000" in length, and so 

 situated that the axis of the epithelial scales 

 or cells is at right angles to the surface upon 

 which they are placed. Sometimes the sub- 

 jacent cells are of a rounded form. 



Cylinder-epithelium is met with in Lieber- 

 kuhn's follicles, and the ducts of the gastric 

 as well as those of all other glands opening 

 into the intestine ; in the lachrymal and the 

 mammary glands; the male urethra; the 

 vas deferens; the vesiculse seminales, the 

 prostatic ducts, with Cowper's and the ute- 

 rine glands. 



3. Ciliated epithelium. In this the form 

 and arrangement of the cells is much the 

 same as in the last ; but their free ends are 

 furnished with numerous vibratile cilia (PI. 

 40. fig. 12). 



Ciliated epithelium occurs in the larynx, 

 trachea, and bronchi; the nares and pha- 

 rynx above the level of the base of the nasal 

 bones, and the cavities opening into them ; 

 the inner surface of the membrana tympani, 

 the Eustachian tube ; the uterus, the Fallo- 

 pian tubes; the lachrymal sac and nasal 

 duct; the palpebral conjunctiva; and the 

 ependyma. 



The epithelium covering the outer surface 

 of the body forms the epidermis or cuticle. 



Further particulars are given under the 

 heads of the organs or tissues in connexion 

 with which the epithelia are found. 



BIBL. Kolliker, Mikrosk. Anat. and 

 Handb. d. Gewebel. ; Valentin, Wagner's 

 Handw. d. Phys., art. Flimmerbewegung and 

 Epithel. ; Henle, Allgemein. Anat. ; Paget, 

 Forbes 's Medical Review, xiv. ; Todd and 

 Bowman, Physiology. 



