CHAPTER IX 

 NASMYTH'S MEMBRANE 



NASMYTH'S membrane, or the enamel cuticle, is a very 

 delicate membrane which can be detached from the surface 

 of the enamel by the action of acids, but which is not other- 

 wise visible to the naked eye. 



The nature of this acid-resisting membrane was for a long 

 time a matter of controversy. It was called by Nasmyth 

 the persistent dental capsule, but this designation does not 

 suitably describe its anatomical relations, as it has been 

 conclusively shown to be in its principal part an epithelial 

 product, and the connective tissue of the capsule appears 

 to have no part whatever in its formation. 1 The view that 

 Nasmyth's membrane consisted of cement was held by 

 Professor Owen, who says, speaking of human teeth (5), 

 the cement ' is thinnest upon the crown, and very gradually 

 increases in thickness as it approaches the end of the fang ; 

 it is only on the implanted part of the tooth that the radiated 

 cells which demonstrate the close analogy between cement 

 and bone exist ; elsewhere the clear basis of the cement 

 alone is present, and this is soon worn away from the 

 enamel of the crown '. It was also considered by Sir John 

 Tomes (9), and afterwards in the earlier editions of the Dental 

 Anatomy by C. S. Tomes, that this membrane represented 

 a thin layer of cement (10) corresponding to the layer of 

 cement covering the enamel in Ungulates. The chief 

 argument in favour of this view brought forward by these 

 authors was that encapsuled lacunae occurred in the fissures 

 of enamel in many instances, the very great overlapping 

 of the enamel by the cement which is occasionally, but 

 rarely seen in human teeth, and which would appear to be 

 of a pathological nature, lending further evidence in support 

 of this view. Professor Huxley (3) considered that Nasmyth's 



1 A paper on ' The Presence of the Sheath of Hertwig in the Teeth of 

 Man, with Notes on the Follicle and Nasmyth's Membrane ', was com- 

 municated to the Royal Society by the author in 1918. 



