INTRODUCTION. IX 



to the structure of the teeth, discovered that the apparent fibres were 

 really tubes, and he communicated a brief but succinct account of his 

 discovery to the Royal Society of London, (1) which was published, 

 together with a figure of the tubes, in the 140th Number of their 

 Transactions. This figure of the dentinal tubes, with additional 

 observations, again appears in the Latin edition of Leeuwenhoek's 

 works, published at Leyden in 1730. The dental substance (dentine) of 

 the human teeth, and of those taken from young hogs is described as 

 being " formed of tubuli spreading from the cavity in the centre to 

 the circumference." He computed that he saw a hundred and 

 twenty of the tubuli within the forty-fifth part of an inch. (2) 



Leeuwenhoek also shows that he was aware of the peculiar 

 substance, distinct from the ivory and enamel, and now termed 

 the cement or crusta petrosa, which enters into the composition of 

 the teeth of the horse and ox (3) ; a component part of the tooth which 

 Hunter speaks of as a second kind of bone ; and which was first 

 accurately and specifically described by Tenon and Blake. 



But these microscopical discoveries may be said to have appeared 

 before their time : the contemporaries of Leeuwenhoek were not 

 prepared to appreciate them ; besides, they could neither repeat 

 nor confirm them, for his means of observation were peculiarly his 

 own : and hence it has happened that, with the exception of the 

 learned Portal, (4) they have either escaped notice, or have been 



(1) Microscopical Observations on the Structure of Teeth and other Bones. — Philos. Trans. 

 1678, p. 1002. 



(2) See Hoole's Translation of the select works of Leeuwenhoek, 4to. 1798, p. 1 14. 



(3) Parvimolares, quos bos, dum ad hue admodum juvenis sive vitulus, habuerat, undiquaque 

 alio osse circumducti erant " Continuatio Epistolarum, 4to. Lugd. Bat. 1689, p- 7. 



(4) Histoire de I'Anatomie et de la Chirurgie, Paris, 1770, Tom. iii, p. 460, in which 



