100 



A MANUAL OF DENTAL ANATOMY. 



cms transparent sheet, upon which, by staining with nitrate 

 of silver, a reticulated pattern may be brought out, as 

 though it were made up of epithelial cells. The inner 

 surface of Nasmyth's membrane is, however, pitted for the 

 reception of the ends of the enamel prisms, which may have 

 something to do with this reticulate appearance. It is 

 exceedingly thin, Kblliker attributing to it a thickness of 

 only one twenty-thousandth of an inch, but, nevertheless, 

 it is very indestructible, resisting the action of strong nitric 

 or hydrochloric acid, and only swelling slightly when boiled 

 in caustic potash. Notwithstanding, however, that it resists 

 the action of chemicals, it is not so hard as the enamel, and 

 becomes worn off tolerably speedily, so that to see it well a 

 young and unworn tooth should be selected. 



Observations upon the presence or absence of Nasmyth's 



Fia. 53 O. 



membrane in fish and reptiles are very much needed ; my 

 own recent investigations upon the development of the 



(*) From a section of a bicuspid tooth in which the cementum, c, is con- 

 tinued over the outside of the enamel, a ; the dentine is indicated by the 

 letter 6. 



