136 EIGHTH REPORT — 1838. 



1683, hacl discovered that the apparent fibres of tooth were, in reality, 

 minute tubes. The tubular structure of ivory was rediscovered by 

 Purkinje and Fraenkel, in 1835, and the disposition of the tubes is ac- 

 curately described and figured by them in the different kinds of human 

 teeth. In these descriptions the tubes are spoken of according to their 

 prima facie appearance as fibres, but their true nature is explained in dif- 

 ferent passages of tlie work*. Purkinje and Fraenkel also added to 

 Dental Anatomy several new and interesting facts relating to the structure 

 of the enamel, pointing out more especially the form and characteristic 

 transverse stria; of the component crystals : and, lastly, they determined 

 the true osseous nature of that distinct layer of substance which had 

 been previously known to surround the fang in the teeth of man, and 

 which thev once observed to be continued upon the enamel of a hu- 

 man incisor. This observation, Mr. Owen proceeded to state, he had 

 confirmed, and he exhibited several sections of the simple teeth of the 

 Mammalia in which both the ivory and enamel were invested by a layer 

 of osseous substance, identical in its structure Avith the cement which 

 enters more abundantly into the composition of the compound teeth of 

 the Herbivora. 



The interesting experiments of Professor Mliller, on the nature and 

 contents of the dental tuhuli were then noticed ; and, lastly, a con- 

 densed analysis was given of the laborious and accurate microscopical 

 observations of Professor Retzius, as related in the original Swedish 

 memoir of that author on the structure of teeth. Besides confirming 

 the fact, that the ivory or bony constituent of a human tooth consists of 

 minute tubes lodged in a transparent medium, disposed in a radiated 

 arrangement, with the lines proceeding in a direction perpendicular to 

 the superficies of the tooth. Professor Retzius has more particularly 

 observed and described the dichotomous branching of the primary 

 tubes ; the minuter ramuli sent off throughout the course of the main 

 tubes into the clear interspaces ; the calcigerous cells with Avhich those 

 fine branches communicate; the terminal ramifications of the tubuli, and 

 their anastomoses with each other, and Avitli calcigerous cells at the 

 superficies of the ivory or bony part of the tooth. Professor Owen also 

 discussed the opinion advanced by Professor Retzius, as to the function 

 of this elaborate contexture of branched and anastomo.nng tubes and 

 cells, in conveying, by capillary attraction, a slow current of nutritive 

 or preservative fluid, through the entire substance of the tooth ; which 

 fluid might be derived either from the superficies of the pulp in the 

 internal cavity of the tooth, or from the corpuscles or cells of the ex- 

 ternal layer of cortical substance or cccmentum, — with the tubes ra- 

 diating from which corpuscles, the fine terminal tubes of the ivory 

 anastomose. Professor Owen concluded the critical portion of his com- 

 nmnication, by explaining the views entertained by Professor Retzius 

 on the analogy subsisting between tootli and bone, which analogy he 

 then proceeded to illustrate by his own observations on the structure 

 of recent and fossil teeth. 



* De Penitiori Dentium Htmanorum Sh'uctura Observationes, VratislavicC, 1835, 



