166 HALL, ON THORACIC CONSUMPTION. 



first plate, afford, I am certain, no little evidence confirmatory of our 

 opinion. 



" At a more advanced period of the disease, when there is a large cavity, 

 the sputa is little more than pus, mucus, large granulous cells, and sometimes 

 portions of opaque tubercle, and confervoid vegetations." 



Dr. Hall's volume is small, and is written in a manner 

 which gives it a claim to be read by all who are interested in 

 the study of tubercular disease of the lungs. 



Ueber die Entwickelung und den Bau des S'dugethierzahns. 

 Von Dr. Adolph Hannover. 



(' Verhandlungen der Kaiserl, Leopold-Carolinschen Akademie,' 

 vol. XXV, p. ii.) 



In this beautifully illustrated memoir. Dr. Hannover con- 

 tributes much interesting information with regard to the 

 histology of the dental tissues in the Mammalia generally ; 

 but we suspect that both by the author, and by the scientific 

 public, the pith of the essay will be considered to lie in the 

 views respecting the development of the teeth, whose expo- 

 sition occupies so large a portion of it. It is to these, 

 therefore, that we shall chiefly direct the reader's attention 

 in the course of the following critical analysis. Dr. 

 Hannover commences his work thus : 



" The dental sac of 3Tammalia contains four elements, which, without 

 coalescing, lie in contact, and are distinguisliable by their very peculiar 

 structure. Below, on the bottom of the sac and coalesced (verwachsen) 

 with it, lies a soft body, which at a very early period acquires the form of 

 the crown of the tooth. This body is the dentine-germ (deutin-keim) ; 

 by a process which we shall call 'deutification' it becomes dentine, a sub- 

 stance characterised by the branched tubules which it contains. The 

 dentine-germ is immediately covered by the enamel-germ : this consists of 

 cells (the enamel-cells), on the whole arranged perpendicularly, which are 

 at first very soft, but subsequently, by calcification, become solid columns, 

 and constitute the hardest substance of the tooth — the enamel. Most 

 externally in the dental sac lies the cement-germ, which, by a process of 

 ossification quite analogous to that which takes place in bone, is changed 

 into cement, characterised by its osteal lacunae and medullary canals. The 

 cement-germ, however, lies in immediate contact neither with the enamel 

 nor with the dentine, but is separated from them by a peculiar membrane, 

 not yet sufficiently distinguished ; this carries upon its inner surface the 

 enamel-cells, which are disposed perpendicularly upon the dentine, and con- 

 sequently it separates the cement-germ from the enamel-germ ; but where the 

 enamel-gcrni ceases it separates the cement-germ from the dentine-germ. 

 We shall term this membrane the memhrana intermedia ; in the complete 

 tooth it appears as the stratum intermediiim." (p. 3.) 



