HANNOVER, ON DENTAL TISSUES. 167 



The careful study aud collation of different passages in 

 Dr. Hannover's work show that his dentine-germ is the 

 dental papilla of English writers ; that the enamel-geroi is 

 the membrana adamantm<2 ; that his membrana intermedia is 

 the layer of what Nasmyth C^ Researches on the Develop- 

 ment^ kc, of the Teeth/ 1849, p. 107) describes as "oval 

 cells/' seated on the deep surface of the stellate tissue of the 

 enamel- organ; and that his cement-germ is nothing mora 

 than the stellate tissue of the enamel - organ, which he 

 confounds with the vascular "actinenchyma" or peculiar con- 

 nective tissue of the proper wall of the dental sac. 



Under the head of the development of the enamel. Dr. 

 Hannover offers us nothing new; but repeats, without 

 bringing forward new evidence, and as if it had never been 

 disputed, the old view that the enamel is produced by the 

 direct calcification of the columnar cells of the membrana 

 adamantin(S. Nor can we find any essential difference 

 between Dr. Hannover's theory of the formation of the 

 dentine and that advocated by Professor Kolliker and others, 

 except that he denies the existence of a membrana prefor- 

 mativa, and affirms that — 



"This so-called membrane is, in my opinion, nothing but the outermost 

 layer of dentine-cells, in which dentification has just commenced." (p. 12.) 



How this can be reconciled with the unquestionable facts 

 that the membrana prefor mativa can be traced with great 

 ease, uncalcified, on to the primary cap of dentine, and that 

 it is a structureless membrane in which no trace of cells has 

 ever yet been detected, we know not ; but we are inclined to 

 suspect that Dr. Hannover has never seen the true membrana 

 preformativa. 



As regards the membrana intermedia we are desirous to do 

 Dr. Hannover no injustice in endeavouring to explain, what 

 seems to us to be, his erroneous view of its functions and 

 homologies in the adult tooth, and we will therefore cite his 

 account of it at length. 



" 4. Membrana intermedia. 



"I have bestowed this name upon a membrane which has not as yet 

 received sufficient attention.* It is a fine and delicate membrane, which 

 must not be confounded with the membranous expansion of the enamel- 



* Kolliker has, perhaps, figured it in his ' Mikroskopische Anatomic,' 

 p. 99, fig. 211 d, without, however, recognising its true nature. What 

 Tomes has termed " basement membrane" appears to have been not exclu- 

 sively the membrana intermedia. _ 



VOL. V. P 



