121 



Aprils, 1851. 



Professor Thomas Bell, Sec. R.S., in the Chair. 



The following papers were read : — 



1. On the Structure of the Teeth of the American and 

 Indian Tapirs. By John Tomes, F.R.S. 



(Mammalia, PI. XXIX.) 



It is now upwards of fifteen years since the attention of physiolo- 

 gists and comparative anatomists was drawn to the structure of the 

 tissues which enter into the composition of the dental organs. In 

 16/8 Leeuwenhoek communicated a paper to the Royal Society, on 

 the Structure of the Teeth and other Bones, in which he described the 

 dentinal tubes. His researches, however, were not confirmed by sub- 

 sequent observers, and indeed were almost entirely overlooked until 

 the period to which I have referred. Purkinje, in 1835, confirmed 

 the correctness of Leeuwenhoek' s observations, at the time uncon- 

 scious that the tubular structure of the dentme had been previously 

 recognised. He also described the structure of the cementum. 



Prof. Retzius was in the same year engaged in examining the 

 structure of the dental tissues, and published the results in 1836. In 

 1837 Prof. Retzius published a work on the subject, the substance of 

 which was in 1839 printed in our own language by Mr. Nasmyth. 



In the latter part of 1837 I was engaged in examining the dental 

 tissues, at that time unconscious that the subject had occupied the 

 attention of the German or Swedish anatomists. In June 1838 the 

 results of my examination were read before the Royal Society. In 

 September of the same year. Prof. Owen read a paper on the Structure 

 of the Teeth, before the British Association. In 1840 the pubhcation 

 of Prof. Owen's ' Odontography ' was commenced, and completed in 

 1845. In this work will be found descriptions of the structure of 

 the teeth of animals belonging to each division of Vertebrata. 



In these various essays the authors agreed generally in the main 

 facts of dental structure, and in each successive publication new facts 

 were related. Judging from the amount which had been published, 

 it might have been concluded that the subject was well nigh ex- 

 hausted. Such however was not the case : many blunders, in the 

 hurry which is incident to a new subject, had been committed and 

 required correction, while many important facts had failed to be recog- 

 nised. Prof. Owen pointed out that in the Order Edentata the teeth 

 are destitute of enamel, while it is present in the other mammalian 

 orders, with the exception of a few isolated cases. 



Having neglected the subject of dental structure for some years, 

 in consequence of more urgent })ursuits, in 1 84 7 I agam entered on 

 the inquiry, which to me possessed great attractions, not only on 

 account of various modifications which are to be found in the arrange- 



