SECT. 142.] INVESTIGATION OF THE TEETH. 3 1 I 



cuticle, which is beset with the growing organisms (an infusorium, similar to 

 vibrio, which Ficinus calls dentieola, also fungi, Uptothrix buccalis [Erdl, 

 Klenke, Tomes, Kblliker] ), first loses its calcareous salts, and then breaks up 

 iuto angular, cell-like particles, as if it had been treated with hydrochloric 

 acid. The same process then advances through the enamel to the dentine, 

 always softening it first, so that it contains only ten per cent, of ashes 

 (Ficinus), and then disintegrating it. The dentine suffers more than the 

 enamel ; and its tubes first become filled with the fluid arising from the 

 decomposition, which may be conducted to the pulp and cause pain, unless, 

 as Tomes found, the dentinal tubes in the adjoining healthy portions are 

 obliterated by deposit, or the pulp is protected by a new formation of dentine 

 in the cavity (Ficinus, Tunics). Subsequently, a brownish matter is deposited 

 in the tubes, and then the intermediate substance breaks down completely. 

 In this manner, the process of destruction advances further and further, until, 

 at length, the crown breaks down, and the fang also loosens and falls out. 

 In jaundice, the teeth not unfrequently assume a slightly yellow colour, which 

 is occasionally almost as deep as that of the skin, and they are said to be 

 often red in suffocated persous, both of which phenomena can only be ex- 

 plained by the passing of the colouring matter of the bile and blood into the 

 dentinal tubes. In rickets, the teeth remain unaffected. In the mucus upon 

 the teeth, the leptothrix buccalis is always to be found growing abundantly 

 in a finely granular matrix, which surrounds mucous corpuscles or epithelial 

 plates ; in it we also meet with the infusoria of the carious teeth, and earthy 

 deposits from the fluids of the mouth. When this mucus collects in larger 

 quantities, it hardens and forms the tartar of the teeth, which, according to 

 Berzclius, consists of: earthy phosphates, 79-0; mucus, 12-5; ptyalin, 10 ; 

 organic matter, soluble in hydrochloric acid, 7-5. 



For the investigation of the teeth, fine polished sections and preparations 

 softened in hydrochloric acid are of service. Since fine sections may be 

 readily obtained in England by purchase, we shall not enter further here into 

 the method of preparing them. Tf it be desired to obtain an entire tooth so 

 soft that the tubes may be isolated, it must be allowed to lie for about eight 

 days in concentrated hydrochloric acid ; thin sections of the tooth-cartilage 

 are then to be treated, from twelve to fourteen hours, with sulphuric and hydro- 

 chloric acids, and some hours with diluted caustic soda and potass. It is also 

 very instructive, to macerate thin sections in acids, and to examine them 

 from time to time upon a plate of glass, till they are completely disintegrated. 

 Prisms of enamel may be easily isolated in growing enamel ; the transverse 

 lines are best seen by touching with hydrochloric acid, and the transverse 

 sections of the prisms may be tolerably well seen upon longitudinal sections 

 of certain layers. The commencement of the teeth-rudiments is to be studied 

 in embryos of two, three, and four months, with a simple lens, on cross sections 

 of the parts hardened in spirit. The structure of the tooth-sac and the for- 

 mation of the teeth, in foetuses of four, five, and six months, and in newly- 

 born infants, in fresh subjects, and, for the relations of the enamel-organ, also 

 in alcohol preparations, in which, also, its structure is well preserved. The 

 pulp of the fully-developed teeth is obtained by breaking them in a vice, and 

 their nerves are best seen on the addition of diluted caustic soda. 



Literature. — L. Fraxkel, De Penitiori Dentium Humanorum Structurd 

 Observations, Vratislav, 1835. A. Eetzics, in Mull. Arch,, 1837. J. Tomes, 



