108 MANUAL OF HISTOLOGY. 



The middle membrane is a peculiar cellular network, formed 

 by the transformation of the middle epithelium layer into a 

 network of cells, below which there is a deposit of a hyaline 

 material. The inner membrane is formed of cylindrical epithe- 

 lial bodies, which are called enamel-cells ; outside of them are 

 one or more layers of polygonal cells ; they form the stratum 

 intermedium of Hannover. The outer membrane is composed of 

 several layers. Finally, the middle membrane disappearing, the 

 outer and inner membranes are brought into close apposition. 



Development of tlie enamel. This is formed by the enamel- 

 cells (inner epithelium, Kolliker), presumably in the same 

 way as the dentine by the odontoblasts. There is a direct con- 

 version of the outer extremities of the enamel-bodies into en- 

 amel. Kolliker, Hertz, and Kollmann, however, regard the 

 enamel as an excretion from the enamel-cells. The former 

 view appears the more natural, especially as the enamel-prisms 

 are continuous with the enamel-cells, having the same form and 

 shape. The successive stages of growth, it is believed, give 

 rise to the transverse markings. 



Whether or not, in the interstitial substance of the enamel, 

 there are corpuscular elements (Boedecker), is a matter that 

 will require further investigation. The outer membrane even- 

 tually gives rise to the cuticle covering the enamel. 



The development of the cement takes place precisely as 

 bone is produced, viz., from the periosteum, or, which is the 

 same in this instance, from the fibrous tissue of the tooth-sac, 

 the periodontium. 



BIBLIOGRAPHY. 



The following systematic works and journal articles may be consulted : 

 RETZIUS. Miiller's Archives. 1837. 

 NASMYTH. Med.-Chir. Trans. Vol. 22. 1839. 

 KftLLiKER. Man. of Human Histology. 1853. 

 WENZKL. Arch. d. Heilkunde. 1868. 

 HKNLE. Anatomie. 1871. 



STRICKER. Manual of Histology. Am. Ed. 1872. 



TOMES. Manual of Dental Anatomy, Human and Comparative. Lond., 1876. 

 OWEN. Comparative Anat. and Phys. of Vertebrates. 1866. 

 BOEDECKER. Dental Cosmos. XXL, 409 416. Phil., 1879. 

 HEITZMANN. Microscopic Anat. of Human Teeth. Med. Rec., N. Y 1879. XV. 



187. 

 KLEIK . Atlas of Histology. 187980. 



