INTRODUCTION. XIU 



tively examined the fractured and polished surfaces of the ivory part : 

 he determined the exact arrangement, course, and size of the 

 tubuli in the teeth of different animals, and detected the finer rami- 

 fications given off by the tubuli during their divergence, (1) and the 

 anastomoses of their finest terminal branches with the cells in the 

 intertubular, or as it is sometimes termed, interfibrous tissue. 



Retzius also claims to have discovered the radiated or purkin- 

 jian corpuscles (2) in the dentine ; and to have thus succeeded in dis- 

 playing a far greater identity between tooth- bone and proper bone 

 than had been before anticipated. 



He exhibited the preparations and drawings illustrative of these 

 interesting observations to Berzelius, Urede, and Professor Wahlberg 

 at the latter end of 1835; being then unacquainted with the disco- 

 veries of Purkinje ; and communicated his researches to the Royal 

 Academy of Sciences at Stockholm on the 13th of January, 1836. 

 They were published in the same year in those Transactions and in 

 the following year as a distinct treatise (3). 



At the early part of that year, 1837, I received from Mr. Darwip 



(1) Leeuwenhoek appears to have suspected the existence of such branches ; he says," upon 

 examining the tubuU round about this small cavity (the pulp-cavity') I perceived that they all 

 arose from thence and spread themselves all round towards the circumference. I endeavoured 

 to examine still farther, beyond the part where this cavity ended, in order to discover whether 

 from these first-formed tubuh others might not arise or branch forth ; but this part of nature's 

 work was inscrutable to me." Hoole's Leeuwenhoek, 4to. p. ] 13. 



(2) J have not yet been able to detect the radiated cells or corpuscles in the dentine of the 

 horse's tooth, in which they are described by Retzius ; but they are very numerous and con- 

 spicuous at the peripheral portion of the dentine of the dugong's grmder, pi. 94. 



(3) Mikroskopiska Undersokningar bfver Jadernes sardeles Tandbenets struktur : Stock- 

 holm, 1837. 



