1 30 Proceedings of the British Association. 



ral fibres of the tooth. The diameters of the two sets of fibres exactly 

 agree. The projections on the formative surface of the pulp cor- 

 respond to the centres of the cells, may be traced to belong to 

 their structure, and are evidently fibres passing upwards from the 

 pulp. Mr. Nasmyth has also ascertained that the fibres of perfect ivory 

 resolve themselves by decomposition into similar granules. He has not 

 discovered the manner in which the osseous matter is deposited in the 

 cells of the interfibrous substance, but he has observed that these cells 

 are subdivided into minute cellules, for they present the appearance of 

 being filled with smaller cells in certain progressive stages of develop- 

 ment. But in whatever aspect, said he, we view the formative organs of 

 the tooth and the dental tissues, themselves, and whether we examine 

 the latter during the process of their development or after their forma- 

 tion has been completed, we are everywhere met by appearances which 

 denote a cellular or reticular arrangement. Mr. Nasmyth concluded his 

 paper by a notice of Schwann's work on the cellular character of pri- 

 mary tissues, dwelling on his views of the cellular organization of the 

 pulp, from which his own were essentially different. 



Saturday. 



Dr. Ludwig Guterbock exhibited a number of instruments made from 

 ivory, softened by the removal of the earthy matter by the action of 

 dilute acid. In a brief memoir on their origin, he showed, that the first 

 idea of the preparation was not due either to the German or Parisian 

 individuals who had claimed the honour, as it was contained in an Eng- 

 lish work, published some time ago, under the title of ' Useful Arts and 

 Inventions.' 



Mr. Nasmyth read a paper ' On the Structure of the Epithelium,' 

 which he described as being composed of cells. He first alluded to the 

 views of Leewenhoek on the subject, contained in letters to the Royal 

 Society, written in 1674, and 1684-5, and according to which, this tissue 

 is composed of scales. The researches of subsequent inquirers tend to 

 prove that scales or cells of various forms exist on the surface of all mu- 

 cous and serous membranes, on the inner membrane of the vascular 

 system, &c. Mr. Nasmyth described the epithelium as a layer of sub- 

 stance destitute of vessels, covering the vascular surface of mucous 

 membranes. The scales, as they were first termed by Leewenhoek, of 

 which it is composed are flat bodies, with a thick portion or nucleus in 

 their centre, and with very thin and transparent margins, which are 

 sometimes curved ; their surface often presents numerous transparent 

 points, with very fine lines. The nucleus of the scale generally contains 

 a small body, which has been called the nucleus-corpuscle. If the secre- 

 tion be removed from an irritated mucous membrane, these bodies are 

 found to assume the appearance of cells, but generally at the surface 

 they resemble scales, from having increased in size, and undergone 

 compression. In the foetus, the well-defined scales of the epidermis are 



