TRANSACTIONS OF THE SECTIONS. 135 



working in warm rooms, and throwing off his clothes when heated. 

 His disease proved fatal on the 18th May. 



The symptoms of treatment of each case, and the post mortem exa- 

 mination of the latter by Dr. Elliot, were fully described. 



On the Structure of Teeth, and the resemblance of Ivory to Bone, as 

 illustrated by microscopical examination of the Teeth of Man, and of 

 various existing and extinct Afiimals. By Professor Owen, JF.R.S. 



Mr. Owen commenced by showing, that he had availed himself of 

 the advantage afforded by the British Association, viz. that in the com- 

 munications brought before a sectional committee, a fuller and more 

 detailed retrospect of the progressive steps which have led to any re- 

 markable discovery, is not only permissible, but peculiarly congenial to 

 its general views and objects ; and he therefore entered into a full de- 

 tail of the recent investigations, especially those of Purkinje, Miiller, 

 and Retzius, on the intimate structure of the teeth, and particularly 

 dwelt on the discoveries of the latter author, as regarded the structure 

 of the human tooth. After describing the mode of arrangement of the 

 particles of the earthy salts, which characterizes true bone. Professor 

 Owen proceeded to state, that until a very recent period the analogy 

 of tooth to bone was supposed to extend no further than related to the 

 chemical composition of the hardening material, while the arrangement 

 of this earthy constituent, as well as its mode of deposition during the 

 growth of the entire tooth, were considered to be wholly different from 

 that of bone, and to agree with the mode of growth of hair, and othsr 

 so-called extra vascular parts, with which teeth in general closely cor- 

 respond in their vital properties. He observed, that the supposed 

 proofs of the laminated structure of teeth, derived from the appear- 

 ances presented by the teeth of growing animals, fed alternately with 

 madder and ordinary food, and by those which often occur during 

 the progress of decomposition of certain teeth, which are then resolved 

 into a series of concentric or superimposed laminae, were equally ap- 

 plicable to true bone, and were quite unavailable in illustrating the 

 point under consideration ; and that the appearances presented by the 

 superficies of vertical sections of teeth, viewed with the naked eye or a 

 low magnifying power, were due, not to the intervals of separate and 

 superimposed lamellae, but to the different refractions of light, caused 

 by the parallel undulations or alternations of structure of minute tubes 

 proceeding in a contrary direction to the suppo&ed lamellae. This ap- 

 parent lamellated structure, however, is not constant, nor equally plain 

 in different teeth ; on the contrary, the fractured surface, or the polished 

 section of the human and many other teeth, presents a silky or irides- 

 cent lustre, which has attracted the attention of several anatomists. Pro- 

 fessor Owen observed, that Malpighi, in whose works may be detected 

 the germs of several important anatomical truths, which have subse- 

 quently been matured and established, conceived that the teeth were 

 composed of minute fibres reticularly interwoven ; and Leewenhoek, in 



