HANNOVER, ON DENTAL TISSUES. 169 



however, the cement-germ as a rule does not ossify, but becomes abortive 

 ou the crowns of teeth with conical dentine-germs, the membrana intermedia 

 iu such crown lies free, and in teeth which have not been worn forms what 

 Kolliker terms the cuticle of the enamel." 



Dr. Hannover then goes on to speak of the identity of his 

 stratum intermedium with the "persistent capsule" of Nasmyth; 

 and he describes the mode of raising up the membranous 

 stratum intermedium in young teeth^ by the action of dilute 

 acids, which he states to have been discovered by Erdl in 

 1843. 



Dr. Hannover appears to be unaware that this persistent 

 capsule, or "Nasmyth's membrane," has of late been the subject 

 of special investigation on the part of Professor Huxley, M. 

 Lent, and Mr. Tomes, and therefore he does not attempt to meet 

 the ob^dous objections which an acquaintance with the known 

 relations of Nasmyth's membrane in the young dental sac would 

 have suggested. Inasmuch, in fact, as Prof. Huxley's state- 

 ment, that Nasmyth's membrane lies on the inner side of the 

 cells of the membrana adamantincB, between these and the fibres 

 of the enamel, has been confirmed both by M. Lent and by 

 Mr. Tomes, it Avill probably be admitted to be correct ; and 

 consequently the membrana intermedia of Dr. Hannover, 

 which lies outside the cells of the membrana adamantine, and 

 is separated by their entire length from Nasmyth's mem- 

 brane, can have nothing to do Avith the latter. In fact, we 

 believe that the " membrana intermedia^' is an entu'ely tran- 

 sitory epithelial structure, and enters in no way mto the 

 composition of the tooth. 



We must express the same opinion with respect to the 

 " stellate tissue " — Dr. Hannover's cement-germ. Dr. Han- 

 nover, after giA'ing an account of the early changes of the 

 epithelial lining of the dental sac, and the production of the 

 stellate cells, in a manner not essentially difli"erent from that 

 contained iu Mr. Nasmyth's last work, seems to us to make 

 the mistake which has already been committed by more than 

 one writer on these subjects, of supposing the actinenchyma 

 of the thickened Avail of the dental sac to be a later stage of 

 the stellate epithelial tissue — A\ith which it has nothing to do, 

 and from which it is separated by the basement membrane 

 of the dental sac. We have in our possession figures, drawn 

 long ago, of sections of the thickened wall of the dental sac, 

 iu all essential respects corresponding with Dr. Hannover's 

 fig. 13 ; and having worked carefidly over the relations of 

 the actinenchyma (which is nothing but such connective 

 tissue as may be met Avith in any soft young organ), Avith 



