TONGUE OF PERAMELES NASUTA. 85 



(4) A narrow layer of very attenuated cells, still granular, 

 and usually having no trace of a nucleus. This layer appears 

 to be more constant in the posterior papillae. 



B. Deeply staining cells : 



(5) A narrow layer of attenuated, deeply staining, finely 

 granular cells with no nuclei. 



(6) Homogeneous, swollen, fusiform cells, very deeply 

 staining, and rarely containing faint traces of a nucleus, as a 

 stellate mass, commoner in the anterior papillae. 



The demarcation between a and b is extremely sharp, and 

 the cells which are at length formed at the surface, after such 

 varied changes, are wonderfully like those formed by the 

 simpler transitions of the ordinary epithelium outside the 

 papillae. This epithelium is of the normal stratified type, and 

 its cells have very distinct nuclei. Traces of karyokinesis 

 can be distinguished in the lowest layer. The superficial 

 cells only differ from the highest cells within the papillae in 

 possessing nuclei and in staining rather less deeply. 



The hair-like papillae are formed of cornified fibre-like cells 

 derived from three sources. First, from the small secondary 

 papillary processes on which each is situated. The rapid 

 transition from columnar and polyhedral forms to cells with 

 apparently vacuolated nucleus, and finally to vertical fibres in 

 the axis of the hair-like papillae, is well seen in a vertical section 

 through the side of a papilla. Secondly, the cells within the 

 ring of hair-like papillae apply themselves to the latter on all 

 sides. The cells at all depths and of all the different kinds of 

 structure mentioned, seem to apply themselves to the hair-like 

 papillae, either before or after the emergence of the latter at 

 the surface. Thirdly, the external cells of the regular strati- 

 fied epithelium of the tongue apply themselves to the outside 

 of the hair-like papillae. (These three sources are best seen 

 in fig. 8.) Thus the cells are received from different sources, 

 and one of these (the second) is extremely complex. 



As to the explanation of the granular cells, it seems most 

 probable that the appearance is due to the development of the 

 corneous material. It appears that this material (or some 



