INTRODUCTION. XI 



of the tubes were determined. He observed that the white colour 

 of a tooth was confined to these tubes, which were imbedded in a 

 semi-transparent substance, and he found that the whiteness and 

 opacity of the tubes were removed by acids. On breaking a 

 thin lamella of a tooth transversely with regard to its fibres, and 

 examining the edge of the fracture, Miiller perceived tubes pro- 

 jecting here and there from the surfaces ; they were white and 

 opaque, stiff, straight, and apparently not flexible : this appearance 

 is well represented in the old figure by Leeuwenhoek. If the lamellae 

 had been previously acted upon by acid, the projecting tubes were 

 flexible and transparent, and often very long. Hence, Professor 

 Miiller inferred that the tubes have distinct walls, consisting of an 

 animal tissue ; and that, besides containing earthy matter in their 

 interior, their tissue is, in the natural state, impregnated with 

 calcareous salts. 



Thus, the discovery by microscopical examinations that the 

 dentine of the teeth in man and various animals was traversed by 

 minute tubes disposed in a radiated arrangement in lines proceeding 

 every where perpendicularly from the surface of the cavity containing 

 the pulp, may be regarded as established, and to be due principally 

 to the learned and ingenious Purkinje, who, however, was all the 

 while unconscious that he had been anticipated, as to the main fact, 

 a long time before, by Leeuwenhoek. 



But the tubular structure of ivory is not the only important 

 fact in dental anatomy, made known in the Breslau Thesises 

 of 1835. Purkinje also discovered that the distinct layer of 

 substance, previously known to surround the fang of the simple 

 teeth of man and many mammalia, contained corpuscles like those 



