SECT. 141.] DEVELOPMENT OF TISSUES OF THE TOOTH. 305 



Fig. 129. 



the newly-born infant, or, on the other hand, only o^"' to 0-2'". At this 

 period, it also possesses vessels in its outer third; and its mesh-work has 

 become metamorphosed into true connective tissue (fig. 129). Upon the 

 inner side of the spongy tissue of the enamel- 

 organ, there is situated the so-called enamel- 

 membrane, membrana adamantines (Maschkow), a 

 genuine cylinder-epithelium, with cells which 

 measure o - oi2"' in length, o'ooi"' in breadth, are 

 finely granular and delicate, and contain elon- 

 gated, round nuclei, often situated at the apices 

 of the cells. 



The development of the tissues of the tooth has 

 always been regarded as a very difficult subject 

 of inquiry. The phenomena appear most simple 

 in the enamel, and all authors have, hitherto, 

 assumed with Schwann, that the enamel-fibres 

 are nothing else than the ossified cells of the Section of the enamel-organ 



i _ i rr 7 t. i from the sac of a molar tooth of 



enamel membrane. Huxley, however, has re- a newiy-bom infant; magnified 

 cently asserted (I.e.) that this cannot be the 250times > a. Dental sac; 6. vas- 



* , ' cular part of the enamel-organ 



case, seem a that the enamel, in all stages of its with a somewhat denser tissue to- 

 development, is covered In, the membrana prce- ae^pon^?^^/^ 

 format) ra of the dental pulp, and separated by it osum '> cd - enamel membrane. 

 from the enamel-membrane. According to Huxley, the enamel is formed 

 independently of the enamel-membrane, and beneath the membrana praeformativa, 



Fig. 130. 





Section of the crown of a human ftetal molar tooth, in which the formation of the 

 dentine and of the enamel has commenced a short time since, a. Tooth-pulp, or tooth- 

 germ, with the vessels ; 6. so-called dentinal membrane, consisting of dentinal cells ; 

 c. fully formed dentine ; d. fully formed enamel; e. membrana praj 'wmativa; e. inern- 

 brana prctformativa (ma is) after treatment with acetic acid. After Lent. 



which is finally converted into the dental cuticle of the fully-developed tooth, 

 discovered by Nasmyth ; still he confesses, that he is unable to give any 

 further explanation of the process. Huxley's observations have been re- 

 peated by one of my most able pupils, E. Lent, and in so far verified, that 

 undoubtedly a delicate structureless membrane may, at all times, be separated 

 from the surface of the developing enamel when treated with diluted acids. 



