TISSUES OF THE BODY. 



143 



Fig. 135. A papilla from the gum of a child, 

 showing the vascular net-work and lamination 

 of the epithelium. 



88. 



The simple pavement epithelia just referred to pass, without any 

 sharp line of demarcation, into the more or less strongly laminated 

 species, through certain intermediate 

 forms. Thus, on the internal surface , 

 of the tympanum and dura mater, 

 and external surface of soft skin, 

 we find an epithelium formed of 

 several layers, but still thin; of 

 these the more superficial are recog- 

 nised as formed of larger and flatter 

 cells. 



The anterior surface of the cornea 

 of mammals affords an interesting 

 example of a moderately laminated 

 epithelium. Here we find from 

 seven to nine layers of cells laid one 

 over the other. The counting of 

 them, however, is not in all cases 

 easy. In some of the strata we 

 observe flattened cells, and in others 

 call bodies, generally of round figure, 

 but often assuming other forms 

 under the influence of lateral pressure. The undermost layer consists 

 of naked elements, greater in height than in breadth, and having each 

 a full, plump nucleus (perpendicularly elongated cells). 



The lining of the urinary apparatus is still less markedly laminated. 

 The uppermost layer is formed of a single stratum 

 of cells of different sizes, with vesicular nuclei. 

 Their under surface displays a varying number 

 of grooves with ridges and prominences situated 

 between them. Applied to these depressions, 

 we find the rounded ends of columnar cells belonging 

 to a second layer. Then follows a third stratum 

 of more irregularly shaped elements, at one time 

 cylindrical, at another, more or less fusiform, next 

 to which, finally, a fourth and terminating* layer of 

 ^mall polygonal cells may be recognised (Linck, 

 Henle). 



The pavement epithelium of many mucous mem- 

 branes of the body often displays much stronger and 

 even very considerable lamination, as for instance, 

 that of the conjunctiva of the eye, the entrance to 

 the naves, the cavity of the mouth and pharynx, 

 as well as the oesophagus down to its connection 

 with the stomach, the vocal cords, and finally, the mucosa of the female 

 genitals, as far up as the uterus. 



For a closer examination of these typical formations, the mouth may be 

 recommended as peculiarly adapted (tig. 135). In the deepest layers, 

 seated immediately upon the fibrous tissue of the mucous membrane, we 

 meet with strata of soft small cells of roundish, or at times more oval 

 figure, with a diameter of only about 0*0075 or 0'0114 mm., and vesicular 



Fig. 136. The so-called 

 spinous or furrowed cells. 

 At a, from the undermost 

 layers of the human epi- 

 dermis ; at 6, from a pa- 

 pillary tumour of the 

 human tongue. 



