70 



felicity which Divine Providence in its wisdom may deign to 

 shovrer down on Your Royal and Sacred Head — is the most 

 ardent wish and fervent prayer of the President, Council, and 

 Fellows of the Royal Societ}', in unison with all your other loyal 

 subjects." 



The following papers were then read, viz. 



" On the structure of the teeth, the vascularity of those organs, 

 and their relation to bone." By John Tomes, Esq. Communicated 

 by Thomas Bell, Esq., F.R.S., Professor of Zoology in King's Col- 

 lege, London. 



Tlie microscopical examinations which the author has made of the 

 structure of the teeth of man and various animals, lead him to the 

 conclusion that their bony portions are formed of minute tubes, dis- 

 posed in a radiated arrangement, in lines proceeding ever^^where 

 perpendicularly from the inner surface of the ca-vdty containing the 

 pulp. These tubuli are surrounded by a transparent material, which 

 cements them together into a solid and dense mass. He finds, by 

 applying the test of muriatic acid, that carbonate as well as phos- 

 phate of lime enters into their composition. In man, the tubuli, du- 

 ring their divergence from their origin at the surface of the central 

 cavity, send off a number of very minute fibrils ; and on approach- 

 ing the enamel or the granular substance, which cover respectively 

 the crowTi and the fangs of the tooth, the tubuli divide into smaller 

 ones, which freely anastomose with one another, and then either are 

 continued into the enamel, or terminate at the boundary between 

 these two substances. Various modifications of this structure, ex- 

 hibited in the teeth of different animals, in the class Mammalia and 

 Fishes more particularly, are minutely described. The granular sub- 

 stance appears to be composed of irregularly shaped osseous gra- 

 nules, imbedded in the same kind of ti'ansparent medium which ce- 

 ments the tubuli together. External to the granular portion, the 

 author finds another substance entering into the formation of the 

 simple tooth, and commencing where the enamel terminates ; and 

 which he describes as beginning by a thin and transparent layer con- 

 taining only a few dark fibres, which pass directly outwards ; but 

 assuming, as it proceeds towards the apex of the fang, greater 

 thickness and opacity, and being traversed by vessels. 



External to the enamel, and in close connexion -udth it, in com- 

 pound teeth, is situated the crusta petrosa, a substance very similar 

 to the bony layer of the simple tooth. It contains numerous cor- 

 puscles, and is traversed by numerous vessels entering it from with- 

 out, and anastomosing freely with one another, but terminating in 

 its substance. These investigations of the structure of the different 

 component parts of teeth, furnish abundant evidence of their vascu- 

 larity and consequent \itality. 



" On the evolution of Niti'ogen during the growth of plants, and 

 the sources from whence they derive that element." By Robert Rigg 

 Esq. Communicated by the Rev. J. B. Reade, M.A., F.R.S., &c. 



In this communication the author follows up liis inquiry into the 



