X INTRODUCTION. 



designedly rejected by all anatomists until the time of the confir- 

 mation of their exactness and truth by Purkinje in 1835. 



The results of the laborious investigations of this most original 

 and indefatigable observer were published, as is the custom in many 

 German Universities, in two inaugural thesises, the one by Fraenkel 

 entitled ** De penitiori dentium humanorum structura observationes ;" 

 the other by Raschskow, entitled " Meletemata circa dentium 

 evolutionem ;" both of which were defended in the University of 

 Breslau in the month of October, 1835. 



Purkinje states that the dentine (zahnsubstanz, substantia dentis) 

 consists, not of superimposed layers, but of fibres arranged in a 

 homogeneous intermediate tissue, parallel with one another, and 

 perpendicular to the surface of the tooth, running in a somewhat 

 wavy course from the internal to the external surface ; and he 

 believed these fibres to be really tubular, because on bringing ink 

 into contact with them, it was drawn in as if by capillary attraction. (1) 



Upon the publication of this discovery it was immediately put 

 to the test by Professor Miiller, by whom the tubular structure of the 

 ivory was not only confirmed, but the nature and one of the offices 



Leeuwenhoek's Letter to the Royal Society is noticed as follows : " Les dents sont composees de 

 tres petits tuyaux transparents et etroits, dont six ou sept cents egalent a peine un poll de la 

 barbe." The merit of directing the attention of anatomists to Leeuwenhoek's discovery of 

 the structure of dentine is due to Retzius. 



(1) Cruorine extravasated during intense inflammation of the pulp, or by an over-disten- 

 sion of the vessels produced mechanically as in hanging or drowning, would in like manner be 

 carried, with the plasma, into the dentinal tubes, and occasion red spots in the tooth-substance ; 

 the bile-stained serum, in the case of jaundice, would equally affect the capillary tissue of the 

 tooth with its peculiar tinge ; but it does not follow that the tubes which imbibe such coloured 

 fluids must necessarily be capillary blood-vessels, and these phenomena, therefore, afford no 

 proof of the vascularity of human dentine. 



