NASMYTH'S MEMBRANE 



335 



There are certain appearances in many of these specimens 

 not described by Dr. Paul in his original papers, and very 

 difficult to explain on the assumption that the epithelial 

 cells are those of the external epithelium of the enamel 

 organ only, as they have previously been considered to be. 

 These appearances can be, we think, clearly accounted for 

 if Nasmyth's membrane is viewed in connexion with the 

 follicle and studied in longitudinal section. 



The clear layer is in direct contact with the enamel, and, 



FIG. 222. Nasmyth's membrane, floated off the enamel in acid. 

 Cellular and clear layers. Clear layer showing impressions of enamel 

 prisms. (x250.) 



as stated above, was considered by Kolliker to be a final 

 product of the enamel cells, although he apparently did not 

 recognize the double nature of the membrane. 



Whether this be so or not it is difficult to say, but in the 

 longitudinal sections a clear layer is often seen on the under 

 side of the detached enamel organ cells, and refractile 

 particles of enamel which have escaped complete decalcifica- 

 tion are attached to it. This might suggest that the clear 

 pellicle represents a membrane corresponding to the ' mem- 

 brana pref ormativa ' of Huxley or the internal ameloblastic 

 membrane of Leon Williams. 



