liv 



SCALY EPITHELIUM. 



Fig. XXI. 



the serous membranes ; but in some situations, and especially in the arteries, 

 the flattened cells, together with their nuclei, assume an oblong fusiform 

 figure, and sometimes their outline becomes indistinct from blending of 

 neighbouring cells. 



A scaly epithelium, in which the cells form several layers, (thence named 

 stratified) covers the skin, where it constitutes the scarf-skin or 

 epidermis, which, together with the hairs and nails, will be afterwards more 

 fully described. In this form it exists, also, on the conjunctival covering 

 of the eyeball ; on the membrane of the nose for a short distance inwardly ; 

 on the tongue and the inside of the mouth, throat, and gullet ; on the vulva 

 and vagina, extending some way into the cervix of the uterus ; also (in both 

 sexes), on a very small extent of the membrane of the urethra, adjoining the 

 external orifice. It is found, also, on the synovial membranes which Hue 



the joints. Its principal use, no doubt, 

 is to afford a protective covering to 

 these surfaces, which are almost all 

 more or less exposed to friction. 



The cells in this sort of epithelium 

 become converted into broad thin 

 scales, from 8 -}^ to - 5 ^ of an inch in 

 diameter, which are loosened and cast 

 off at the free surface. Such scales, 

 both single and connected in little 

 patches, may be at all times seen with 

 the microscope in mucus scraped from 

 the inside of the mouth, as shown in 

 fig. xxi. ; but to trace the progressive 

 changes of the cells, they must be suc- 

 cessively examined at different depths from the surface, and the epithelium 

 must also be viewed in profile, or in a perpendicular section, as exhibited in 

 fig. xxn. 



The deepest cells, or those next the subjacent tissue, are sometimes 



Fig. XXII. 



Fig. XXL EPITHELIUM-SCALES PROM 



THE INSIDE OF THE MOUTH ; MAGNI- 

 FIED 260 DIAMETERS (Henle). 



Fig. XXII. EPITHELIUM FROM THE CONJUNCTIVA OF THE CALF, FOLDED so THAT THE 



FREE SURFACE FORMS THE UPPER BORDER OF THE FIGURE, AND RENDERED TRANS- 

 PARENT BY ACETIC ACID. 



1, 2, 3, 4, 5, progressive flattening of the cells as they rise to the surface. The 

 outline figures represent single cells from different depths, viewed on their surface ; and 

 at 4' and 5', edgeways. Magnified 410 diameters (chiefly after Henle). 



